I agree with you on that...
Take Halo 3 as an example...There was so many updates prior to the release that when the game was released you would pretty know much everything, apart from the main storyline of course.
The last major release into the addition of GTA games was in 2004/2005 with San Andreas. If you think about it, Rockstar is bound to have finished developing the game, going through it for bugs, and all that stuff. The only thing they haven't done yet is marketing...Sure they have the official website for the game, they do advertise it in game stores (I asked a salesman at GW once when it was being released and he said April 2008) but there is just too little information about the game like Jace said. We've only got 3 trailers to watch, there are NO gameplay videos where we can get a taste of the HUD layout and how it will look like and there are unconfirmed reports circulating the internet. Give us official details, Rockstar!