First instead of posting to the thread, you should READ IT.
That said, it has been stated you can play offline BUT, you will NOT get any new free maps / other content offered (DLC), you will not get any FIXES (patches) to the game, you will not be able to do ACHIEVEMENTS or have them recorded to Rockstar (which is where they maintain such things), also in many cases attaining certain achievements or levels UNLOCKS other things like missions, guns, vehicles etc, but again that needs a ONLINE connection. Further you can't do the BIGGEST feature of the game, MULTIPLAYER unless you have a Internet connection.
Honestly this sort of discussion (being offline to playgames) is something people stopped focusing on back in 2005, games have been (Halo etc being the most famous) all about BEING ONLINE, and now are centered on it to work.