I just read a french article saying british journalists revealed some informations about the game... Maybe fake but I'll quickly translate (french source:
http://www.adobuzz.com/news/39695-gta-5-journalistes-anglais-spoiler-jeu.html )
Map at least 4 times bigger than IV's LC.
There'll be malls and university campuses, and a huge hospital.
Lots of secondary characters, no children, there'll be animals but not sure if we'll be able to kill them.
Weather from heavy rain to boiling hot (nothing new, maybe heavier rain than before?)
The character will be a black american of about 30years old, and we'll be able to change weight and clothes.
We'll be able to catch other people and use them as a shield or hostage.
There'll be customisable weapons, axes, swords that can be stolen in a museum. Cops will be better than before and use tear gas.
A few mini games, bowling, basket ball, climbing, swimming, and 2 others that idk how to translate.
We'll be able to upgrade cars, and we'll have to fill the gas tanks (I really hope it's not a fake fort that).
But I doubt a lot about it being a serious articles, especially for the name of the website (teenbuzz) and there are some spelling mistakes..
Btw, after 1:05 on the trailer, do you think it's CJ getting chased by cops? imo no because he should look older, but I've seen a couple of comments saying that's him...