It would be nice if it were 1 city in USA, 1 city in Europe and 1 city in south america. Then you could travel by boat or plane between them.
I hope the GTA IV will take place in the 2000's or maybe the late 90's.
And I would also like an idea where you follow a character through a trilogy. It could start in the 70's, where the character would be aged 20-25. Then the next GTA could be set in the 80's-90's then the last one in present time.