GTA has never been released the same year it was announced, R* always seem to announce it at a 3/4 mark of the games progress in development. I'm assuming that the map itself is still being touched up, aswell as optimization for a steady frame rate considering they will want to make it bigger and better than IV... I think the most we will get is an announcement and maybe a trailer but that will either be April or further down the track judging by R*s habits. Knowing that R* have sorted out all the physics and GTAs R.A.G.E engine, less time is needed for developement, GTA V's developement would've began just as IV went gold, but even then it was announced that the Rockstar team that made IV were given a break from all development. GTA IV began development as San Andreas was just getting its final touch ups.
Its also a stupid marketing decision to release something as big as GTA the same year of its announcement, Rockstars well known for getting the very last drips out of hype from its fans. They would want a lot more time to show it off and gain as much attention as possible before they even think about giving a release date. Look at all the teaser and trailers before GTA IV... A year before it was released. No 2011 release for GTA V, 2012... Thats more like it.