I think that they should develope the other cities that were in SA and turn them into another game like TBOGT, or make them downloadable content. It would make the next 5 year wait for GTA VI much more bearable. And car customization should come back, BIG. I want to be able to put different paint jobs, rims, engine upgrades, bulletproof tires/windows, ect...
And I also want to be able to dress up as a cop to do the vigilante missions. And instead of just killing them, maybe we can shoot their knees out and arrest them. And pull cars over and arrest them. I know it would be difficult to fit into the button lay out (walk up behind Someone and press the action button to make an arrest) but I think it would be fun to arrest someone in the city, drive to the top of the mountain and let him out, maybe light him on fire or something >
Last thing, I want to be able to drive around a corner and see a drug drealer, so I shoot him (naturally) and he drops the drugs he was carrying. I can pick that up and sell the drugs to a friend at one location. Same for weapons, I can walk into a Amm-u-nation and sell the guns that I picked up in the last fire fight. Maybe even cars, like on the web in GTA IV they have pictures of cars and the numbers to call to buy the car. But none of them work. I want to be able to actually go to a dealership and buy a car that will always spawn at my safe house or something. I have heard that something like this is in the game. With a underground economy that u can effect, but these are some features that I would enjoy to see in GTA V. And if these are in the game than I probably won't play the game for two months (a pathetically long time for such a empty feeling game like GTA 4) and then never play it again. And to clear that up, I loved GTA 4, but when u beat the story it's mostly finding birds and cars. If I could continue making and spending money after the main story is done, than I think the game will last longer and the wait for GTA VI will not feel like a life time.