I personally feel that it will be heading in the direction of the UK, it ties in with the series much better - mind you though, Tokyo could be a realistic possibility (think of a kinda fast n furious style of racing instead of the big dome stadiums).. The US has been overdone, way overdone - R*, its time to move on from that theme!
Oh yeah, and if you dont think the UK could be funny - watch lock, stock and two smoking barrels or snatch..
I couldnt care less if its a mafia, gang-bang or business storyline, but one thing that needs to stay solid is that the story is based on one particular character!! There is no way that such a cohesive storyline as per previous games in the series, could be followed through with if it was based on a pick n match your own character..
One of the things that has made the GTA series so popular has been its play on real life - the game is completely believable. By allowing every single player a glimpse of something they see in their own world, be it a flannel wearing hick, some hussy selling her arse on the street corner or a regular business suit heading off to work its that reality that makes it work so well. I hate to admit it, but adding hovercars and the like will just push away the people that loved and have stuck with the series since birth..
Then again everyone, R* are known for pushing new genres and trying things nobody has ever thought of before, so R* - just stick with what you believe in and we will be happy!!!