This will never happen to GT series.
Why? Let me give you some guidelines:
- first define the requirements: What kind of mods will be possible for the community to create? Is it simple mods (muffles, different rims, change shade of windows), or do you mean complete mods, i.e., complete design your own car model?
I bet you had the 'complete mods' in mind.
Now in order to truly talk about "no-limit mods" (regarding creating your own car, not some fantasy mods where you can put monsters and that kind of BS in the game), the right tools need to be available to the community.
- Putting these tools on the same disk is going to require a LOT of precious diskspace. This diskspace could've been used for other purposes...
- Putting these tools out on the web where people would have to download them to their computer/pc: then the issue is how do you transfer your model from your computer to the PS3? Where will it reside and how will it interact with the game mechanism if the mod a person created contains bugs? Then there are cracking possibilities and security concerns...
Still assuming you're talking about the "no-limits mods", I bet the graphics have to be in par with the default game graphics as created by the gamedevelopers. Now, what interface should the developers have to create in order to let mods maintain the graphics quality? What happens if a user creates a mod which uses extremely high definition textures? Would the system/hardware handle that?
Third thing: there is no big crowd that is interested in mod-creation for console games. The reason why i believe this, is because there is a difference between pc-gamers and console gamers. Pc gamers tend to know more about computers, design and gaming in general, than do console-gamers.
These are just a handful of questions/issues arising in implementing a new feature in software. I am a serious hobbyist programmer and when I think of a new feature for a program I've created, no matter how small the feature is, a LOT of issues come around the corner for correct implementation of the feature.
So let alone a highly complex feature like mod-creation for big software like a PS3-game.
As long as these mods are 'simple', then sure, i definately see them in the next version of the game.
On the other hand, i'm afraid complex mod-tools will be available only to pc-games.