I definitely hope that Gr. 3 and Gr. 4 are updated for GT7 since a lot of cars currently in these classes now have been replaced/have real-world variants now. I've actually been thinking a lot about this, and it seems that people here have similar thoughts.
I'd rather they sit in their own category rather than being shoehorned into Group 4.
Yeah, I've been thinking a lot about revising Gr. 4, and splitting it where the FF cars get their own sub-class, so there could be a Gr. 4A which is all of the Gr. 4 cars minus the FFs (and possibly converting the AWD cars now to RWD), and Gr. 4B which will be the current FF Gr. 4 cars. This would open up Gr. 4A to use updated offerings such as the Audi R8 GT4 and give a new-subclass where cars like the Civic Type R TCR and the Veloster N TCR can be introduced.
While I am gonna wait until actual new trailers arrive and not expect anything different from PD, there is an overwhelmingly strong case for GR.3 And GR.4 to be redone so here's my take regarding the Manufacturers present:
Alfa Romeo: Either replace the 4C with the Giulia (If its even possible to make a GR.3 version of the Giulia, but then again we had the RCZ and Beetle..) or just don't have the Manufacturer anymore. As nice as the 4C is to look at, its old.
Aston Martin: Well what else needs to be said really? The New GT3 and GT4 Vantage do exist so replace both cars.
Audi: Obviously, one of several cars where its painfully obvious the older car is well overdue to be replaced by the EVO. Likewise, it's time for TT Cup to go (Perhaps not entirely away, but just out of GR.4) and time for the R8 GT4 LMS to replace it.
BMW: While technically the only car not entirely out of date and even still competitive, the BMW M6 GT3 is pretty much on it's way out in real life as the M4 GT3 will soon replace it (Depending on how the financial situation of the pandemic goes) so that naturally means the M4 GT3 should be the natural replacement for GR.3. Think it's a broken record at this point, but the BMW M4 GT4 should naturally replace the M4 GR.4. It's basically the same thing with only the rear wing and hood being the big difference.
Chevrolet: Kind of a tricky one this is for GR.3. On one hand, the Corvette GT3-R would be an actual GT3 Corvette racing against other actual GT3 cars (I believe it is technically a globally homologated GT3, just doesn't race anywhere else but Europe usually) and we don't get more then one GTE car in a class that mimics GT3 (Unless you're roleplaying the Nurburgring 24 or the 24H series, then pretend its just SP9 and SPX). On the other hand, the C8 is the biggest talking point right now and between GM wanting to always showcase the latest thing and the People wanting an actual Corvette Racing car and not another fictional, we would likely have to settle for another GTE car mixed with GT3s. Either way, The C7 GR.3 (like most of the GR.3 class) is beyond old news really. As for GR.4, simple: Camaro GT4.R replaces C7 GR.4 doesn't get any simpler then that and I don't really feel like it'll be missed.
Citroen: No point in having them anymore as the GT by Citroen is outdated as is the GR.4 car and the company literally makes nothing remotely fit for either category so removing them would be better. Even PSA don't do much with them in racing anymore at the moment so PD should take the hint.
Dodge: Even as an old Viper Fanboy, I think the brand is better off gone. Realistically, only the most hardcore fans use it or the GR.4 anymore and being realistic, What is there to even replace it?
Ferrari: 488 GT3 Evo for GR.3, period. Likewise, a 488 replacement for GR.4. Nothing else to be said really.
Ford: This is actually an interesting situation. What direction should be taken here, A facelifted Ford Mustang GR.3 car with a matching GR.4 car (Yes I know there is a Mustang GT4 out there, but its not based on the facelift), or have the Ford GT GTE? It wouldn't be the first time a Manufacturer has had multiple entries (Look at BMW, Mercedes, Lexus, Volkswagen and Peugeot) and people would finally have the GTE like they have been wanting, even though its not racing anymore (Because Ford being Ford).
Honda: Replace this brand with Acura and give us the actual NSX GT3 Evo for GR.3. Even when this car races oversees, its literally just a badge change of the same car made by HPD in the US. GR.4 can either have that car rebadged as an Acura or have the TLX as a GR.4 replacement (maybe even based on the TLX type S Pikes Peak car).
Hyundai: Another brand that needs to be gotten rid of from Manufacturers series. The game came out literally months after production of the Genesis ended so its absolutely dated and the brand has nothing remotely close to replacing is. Only other option I could see is replacing it with the Genesis brand (and use the G70 as I feel that is much closer in form to the old Genesis Coupe).
Jaguar: Not much to it other then update both cars to the new 2021 Facelift. Might be a good opportunity to do some interesting tweaks to the aero as well.
Lamborghini: Just like with Audi and Ferrari, bring the EVO for GR.3. GR.4 car can just be replaced with the Facelift version with a proper drivetrain swap.
Lexus: Obviously the GT3 car is still competing so nothing other then using the latest car I guess until Lexus actually has some sort of evo package in line for it. GR.4 however, they can easily base it off the 2021 RC F or even the RC F Track Edition.
Mazda: RX-Vision GT3 Concept for GR.3 and perhaps replace the much heavier Mazda Atenza with the Mazda 3 for GR.4. That would be my idea anyway.
Mclaren: 720S GT3 for GR.3 and 570S GT4 for GR.4, done and dusted.
Mercedes: EVO for GR.3 and AMG GT4 for GR.4. Again, done and dusted.
Mitsubishi: Remove it, competes with a long killed off car and it has no viable replacement.
Nissan: As much as this is a Brand I feel barely cares about racing anymore, its way past due for a replacement to Kaz's GT3 car from the 2013 Nurburgring 24 with the current GT3 car. GR.4 is fine I guess, just swap out the drive train.
Peugeot: Another brand that is better off not in the Manufacturers Series, no replacements remotely exist and the car being used is beyond dead.
Porsche: 911 GT3R and 718 Cayman GT4 for GR.3 and GR.4, simple.
Renault Sport: Get rid of. Its inclusion in the Manufacturer Series period is just too controversial with not only a car thats only "GT3" in performance (Nothing more then a detuned version of the original) and both GR.4 cars are beyond hilariously placed (FF car being too OP depending on BOP and do I really need to point out the issue with a MR Silhouette car in a class with actual production based cars?)
Subaru: WRX for the current model doesn't seem all that different so GR.3 car is alright for now. I would also possibly suggest the BRZ GT300 if possible as that is something that is actually BOP'd against GT3 cars. GR.4 though, BRZ. Yes its effectively another 86 in GR.4 but read what I have in mind for Toyota and this makes more sense.
Toyota: Perhaps a updated version of the Racing Concept is in order for GR.3. GR.4 though, just get the actual GT4 car. All that needs to be done.
Volkswagen: Kick to the Curb. GR.3 choices make no sense anymore and again, GR.4 doesn't need any FFs.
Again, I don't expect PD to Do ANY of this but its just my thoughts.
I have similar thinking to yours, with the updates/replacements having priority tiers:
High priority: New cars have been introduced in the real world that would add to variety and keep the game up-to-date:
Alpine: Add in the Alpine A110 GT4 for Gr. 4.
Aston Martin: Add in the new GT3 and GT4 Vantage
Audi: Add in the R8 GT4, and if Gr. 4 does get split in the manner I suggested above, this will replace the TT Cup. Otherwise, it will be another Gr, 4 option.
Bentley: I'm assuming licensing is an issue which is why it hasn't shown up in GT Sport, but adding in the Continental GT3 would be a no-brainer if possible, and a fictional Continental Gr. 4 car could be made.
BMW: Even though it'll be "out-of-date" soon, adding in the M8 GT3 would add variety. And of course, adding in its successor the M4 GT3 would be necessary.
Chevrolet: Add in either the C8.R or make a fictional C8 Gr. 3 car, since PD seems to have a hard time getting the rights to the proper Corvette GT3 car since the last one seen was the C5.R. Similarly, add in the Camaro GT4.R or make a fictional Camaro Gr. 4 car. I wonder if Pratt and Miller and PD can't come to an agreement?
Ferrari: Agreed, 488 GT3 Evo for GR.3 and a 488 Gr. 4, which I was surprised wasn't in the game to begin with.
Ford: Even though the program ended it would be nice to have the Ford GT LM for Gr. 3. If the Gr. 4 split above happens, a Focus ST Gr. 4 could be made for that class as well.
Ginetta: Add in the Ginetta G55 GT4 to Gr. 4.
KTM: Add in the KTM X-Bow GT4 to Gr. 4.
Maserati: Add in the Maserati MC GT4 to Gr. 4.
Mclaren: Agreed, 720S GT3 for Gr. 3 and 570S GT4 for Gr.4.
Mercedes: Add in the AMG GT4 for Gr. 4.
Nissan: If the Gr. 4 revision I suggested above happens, the GTR Gr. 4 could be replaced with a 400Z Gr. 4 version to make the Gr. 4 entry RWD.
Porsche: Agreed, add in the 718 Cayman GT4 Gr.4.
Subaru: Adding in the Mother Chassis GT300 BRZ would add another Gr. 3 choice for fun, and a BRZ Gr. 4 could replace the WRX Gr. 4 if Gr. 4 is revised and becomes pure RWD.
Toyota: Add in the Mother Chassis GT300 Prius for Gr. 3, because why not?
Lower Priority: A variant of the car already exists in the game, but is old/fictional and could be updated/replaced:
Audi: Add in the R8 LMS Evo to replace or supplement the current R8 LMS.
BMW: Add in the M4 GT4 to replace the fictional Gr. 4 version, for immersion's sake.
Ford: Add in the Mustang GT4 to replace the fictional Gr. 4 version, for immersion's sake.
Honda: Add in NSX GT3 Evo for Gr. 3 to replace the fictional Gr. 3 version, for immersion's sake.
Lamborghini: Add in the Huracan Evo to replace or supplement the current Huracan GT3.
Mercedes: Add in the AMG GT3 Evo to replace or supplement the current AMG GT3.
Nissan: This is kind of an in-between priority for me, but the current 2013 GTR GT3 car is really old now, with the GTR GT3 having been updated twice since then, so this should be replaced with the 2018 spec car. Although, there is technically a GTR in Gr. 3 still, so that's why it's not the highest-priority in my books.
Porsche: 911 GT3R to replace or supplement the 911 GT3 RSR.