The only thing I can see them adding in the future would be North Yankton & Liberty City (Both touched up & up to date). But honestly? No.
Kinda OffTopic: Regarding to the post above speaking on the "world of GTA Online expanding" I think they're on track with that statement. My bet is that they stick with RAGE, and focus on the map/story/content for the next games to come. IMO this so called "World" might actually come to life. NY/LC can easily be added to the mix as new areas (Through a choice/Airport leading to a loading screen). But maybe we won't see this until the next game & map comes out. Ala, GTA 6 takes place in (Insert City Here) but you can revisit LS/NY/LC that can be downloaded via Marketplace/PSN.
But this takes up a massive amount of resources. PC can surely handle this...but I wonder if X1/PS4 can?
Uhh if they want, the 360/3 can handle it, however barely.
the xbox one and PS4 are 16x stronger/better than the previous generation consoles, they don't have to make any cuts here.
Also, Rockstar isn't pushing the boundaries in GTA V Next Gen. They could easily create a map the size of Europe if they wanted too. Hell look at The Crew. That game has the entire (scaled down) USA in it.
GTA doesn't need a map that size, but they could easily create Northern San Andreas without a performance hit.
If other cities are added which are only accessible by Airport, then they can expand indefinitely.
Also Rockstar wants to expand GTA forever. Including new cities, maps and missions all the time. The map right now just isn't enough to have people play the game for another two years. To let the game stay interesting they NEED to expand the map.
Also it is a continuous stream of money for R*, they are not going to give that away. They are going to expand GTA Online (and V) with new maps, cities and missions for a long time. So people actually stay and play the game, which gives Rockstar a steady stream of money.
Even if you are against it. (or not, I dunno) it is the smartest business move they could do. Release GTA V: Northern San Andreas (or something similar) and sell it for $30/$40.
They could do this forever if they want and players will make R* more and more money.
Why let a successful business model bleed too dead?
ROCKSTAR CONFIRMED IT