Well, with just over a month to go before release, it appears Microsoft have already uploaded the achievement list for Grand Theft Auto V and made it public, good old Microsoft!
The game contains 49 Achievements (50 on PlayStation 3 due to the Platinum), 17 of which will be devoted to Grand Theft Auto Online (Sorry speedrunners, no 100%-ing GTAV within a week of release!), which does reveal new online modes not yet revealed by Rockstar, 11 achievements are hidden and story related with the rest being devoted to gameplay and exploration of the southern San Andreas state, including activities such as Rampages, Stunt Jumps, Weapon and Vehicle Modding and finding SPACE SHIPS??? Well, I guess things are going to get weird.
Once again, the full list does contain some spoilers for the game but if you still wish to check it out then head on over to the Grand Theft Auto V section on Xbox360Achievements.com.