It is less important for me that is takes place in "Los Angeles" since they will change everything again. Whatever memory I have from GTA:SA will be useless.
More important is the fun factor. GTA:IV was sorta fun with a lot of depressing crap. GTA:IV:TLATD was also kinda depressing. GTA:IV:TBOGT was fun fun fun! Who doesn't want to fly a gilded attack helicopter? Or steal a train car? Or hector the Russian muscle guy who never wants to talk?
Unless they put back some of the RPG elements back into this game I won't be buying it. GTA IV was so fucking boring to me. It was essentially a point a to b grindfest with barely anything to do in between. There weren't even any buildings to buy in IV. Money was worthless. Plus fuck LA.
Favorite territory control GTA was SA. I loved beasting like 40 dudes with my M4 to take over territory. I hate buying buildings though. Every gang-territory control game should have an accountant that handles that shit.
Buying the buildings and doing context-sensitive quests to fully own the businesses and generate useful resources is good.
Making the work to get a business be only money and the business only producing money is bad. The player is stuck in a loop when buying properties where money is extremely scarce because there's always more properties to buy, but once they're all purchased the player has nearly infinite money.
I think a GTA where it takes place in not only more than one city, but more than one country would be great. You start in NYC and as you gain prominence you're called upon to meet the big man in Italy and the game continues from there with trips to the Middle East, Spain, England, etc.
Or have an Asian-based GTA. The Yakuza has a ton of material to work with. Make a GTA: Tokyo or something.
I bought it around Black Friday and to be honest, I couldn't get into it... all I played was the first "tutorial" type mission so I really need to invest some time into it before I can give a real opinion on it