All cities and places in GTA Universe would be put together in one massive world map, a megaserver would be implemented and thus all players would play at the same lobby.
Icons are only shown on minimap / city map when firing guns, driving armed vehicles, PvP related events (Random, Ceo, Biker and whatsoever upcomming) and calling Lester to track the player who killed you so you can pursuit him for some ammount of time, cell phones can be exchangeable for new ones with a cooldown so you avoid being tracked, changing phones make you loose the "Player's contact" who's not on your friend list. You can track down Players once you got their contact (can be just by adding his/her name on the contact list) that havent changed their cell phones. (texting and communicating has a purpose now).
Oh, and btw, the character names now shown as the one when you created them, remember that? not your SocialClub nickname.
There are two channels of chat text, City Chat, and World Chat.
Interiors on buildings with apartments and business are all reworked, there are no instanced floors now, say for i.e, you have your office in Maze Bank at 25th floor, you enter the building wihout a loading screen, you get the elevator or stairs and get to your office, some other player that happens to has an office at the same floor, both will be meeting by the elevator, stairs and hall, nice to have neighbors right? Weapons are not allowed in Apartments and Business.
Lets say, with so many thousand players online, you could think that fitting all those players wouldn't have buildings enough for us all right? Take a look again at the map, so many buildings that could have interiors, and only in Los Santos, i know hardware speaking this is a different story, but i know this is a matter of time til happen. ( if not in GTA, in other games will).
Sorry my English, Good Game everyone.