Well, while GTA IV had its criticisms, mainly the more serious nature, and the dating/friends system (which you could switch off and completely ignore), I think it was a landmark game for this generation, I wouldn't be at all surprised if Rockstar impress us all again, I don't see them just churning out GTA 4.01, after all 3 was a fair jump from 2 and 4 a pretty big move up from 3.