There has to be a set number of cars otherwise GT5 will have "unlimited" cars which is impossible.
You must bear in mind that PD don't start the game with a set number of cars, they have a rough target which they will set for themselves in the planning stages but that's not a wall where they say "right we've hit our target, you don't need to finish modelling that Veyron we've licensed, we're not including it". PD strive to include as many cars as they can, cars they have licensed. They don't have licenses to include everything. At the end of the day nothing that's on the disk is replacing anything because if PD had the man power and time they'd include every car they licensed.
"And what if I already had one of the cars and they replaced it in the game so it disappeared from my garage?"
Or they could just remove the 06 Viper from the actual GT5 game before they release it?
That's a stupid idea, why would you want PD to remove sometihng they've spent time and resources in making that can be enjoyed in the game when for less effort you could have both. It stand sto reason that to replace a model with a newer one that the older model must be modelled first liek your Viper example, to suggest that PD then remove the older model in order to include the newer one not only defies logic but it makes no business sense as you'd be constantly just updating models and wasting tonnes of time and money on creating models that are only going to be scrapped anyway.
It doesn't matter if it is DLC or not. PD isn't going to be working on GT5 forever. Also, you have a limited amount of space in your hd anyway.
Disk space is not an issue and neither is HD space. You can always buy more HD space, and if your disk isn't big enough for all the DLC then it's down to you what you delete. The game should not decide that for you.
Hell, if PD includes both versions and the very last DLC update is over, at least someone is going to complain about TWO of the vipers being in the game which one of them is the superior one AND 06 Viper hindered his/her fav car from being in the game.
You're probably right, a small number of stupid people might. People who have more one brain cell vibrating in their heads though might understand that scrapping an already modelled vehicle to include a newer one is stupid when you can have both.
Unless you are not the type of guy who complains about the variants of Skylines in the game, I'd say the 08's 600hp Viper should take priority.
If you don't have a base model already in progress then sure, start from the top with sporty models, but if there is a model already done and then a higher performance model comes out you don't scrap the work you've already done.
On the contrary, I do. Whenever one of my fav. cars is not in the game, I'm going to blame on the variants for excluding mine.
So let me get this right, the game includes the Viper, that's fine, but then the new 08 Viper comes along as DLC and doesn't overwright the old one and that means that because there are two variants that one of them has caused another car to be excluded. But if the new one did over wright the old one it wouldn't
. I'm sorry buit that's the stupidest thing I've heared, seen or read all day and I've just got back from the Cinema to see "The Hangover" and the guys in that do some pretty stupid stuff so that is saying something. I hope you understand that for each car PD need to have a legal right to include it, they can't just decide to. The odds are that if the car you want is a note worthy car that the most likely reason it isn't in is because PD didn't have a license for it 💡. Not because they didn't delete and older model of a car that they had already completled when they made a newer version of the same car.
Mate, you seriousely need to think about what you are suggesting. It's beyond understandable.
So we shall receive six different Corvettes, one for each generation, the newer model in each one. What a fantastic idea! You know what? It's so fantastic I think we should contact PD right away! 
