I think Brotha is right on some of this. Now, I haven't played this game myself but I think that Rockstar have enough confidence to redo the III trilogy inside IV. As, the competition is nothing but Saint's Row and people are crazy about this strategy.
A move out of America I disagree on, until an extent. Sure, take it somewhere into Europe and you'll be confronted with a new GTA feeling, but honestly, Tokyo sounds good. They have the cars (The Fast and the Furious, people!) the kind of crime (Yakuza related) and a pretty dam big city.
As for character, what do you mean, Brotha? I think a Yakuza character would be pretty cool, but anything like Nick Kang of True Crime is stupid.