I read that they were going to base the city around Honk Kong but the roads are to complex. IMO that would be pretty shit. I would like to see another London or even a city in Australia.
London would be cool but what about a town or island such as Tenerife. For that they built GTA 5 is los santos and still couldn't meet real life size due to the size of LA. I think size wise and in game size for example could be a Cuban island, 20x20 mile piece of land.