Well, it's been
said CONFIRMED that Ray Liotta was not the voice in the trailer, which in-turn is raising major doubts about the main character being Tommy Vercetti. Although it still looks like an older version of him (Also a little like Frank West to be honest), it has NOT been confirmed by Rockstar if it was indeed Tommy with a changed voice actor (Doubtful) or if Rockstar will continue their long line of new main characters each game. I guess we will just have to wait for confirmation from Rockstar.
It's also very strange they have not mentioned which platforms the game will be available on, could it be a hint that it may be on Next-Gen Consoles? Maybe. Analysts have projected that a new console may hit shelves by 2013, so the time frame fits with the production of a AAA title.