And the same goes for the next one. They can use things from all three previous games. What's stopping them?
But it still makes more sense to do one game per city. I don't see where people come to the conclusion of 3D'ing all of GTA2. That isn't what they did before, where the hell do you get the idea that they will do that next?
Logical size increases, each GTA has been getting bigger and bigger, and so I thought they would do the WHOLE of GTA2 and it will be huge, one city of GTA2 would maybe be the same size as SA or something.
Thinking about it, it probably will be one city because then it will be the same size as SA but with better graphics, cars and othe stuff