There's no set release date as far as I know, although I can tell you that it will probably be sometime in 2008.

Prologue is out soon, though, but it's only a sort of demo version of the full game. I think the same has been done with all GT games.

Which version of the console are you thinking of getting?

If you want to play PS2 games, then DO NOT get the 40gb, for the sole reason that it has no backwards compatibility at all.

Even if you don't want to play PS2 games, the 80gb console is still the better deal. At least, I think it is - I'm not too up to date on the American bundles, though I can guess that the 80gb will be better value for money.