They're adding GTTV and some serious gameplay tweaks. Their next update is supposed to add tracks and cars... http://www.joystiq.com/2008/07/30/gt5-prologue-update-hits-on-friday/ My only issue is... Why spend all of these resources on this demo thingy??
I read a Q & A with the guy in charge, and he said they had no plans set forth at this time for the actual GT5, everything they are working on is related to prologue. I kind of want to get prologue, but I want to get a wheel and a racing seat too, and I can't really right now.
Yeah I read on n4g that the game could be as late as 2010 (GT5 that is) so it looks like this may end up being the official GT5 (my own assumption) just as Home Beta will probably end up being Home if it ever gets released. If GT5 Prologue isn't indeed GT5 most are saying GT5 is getting pushed back because of like what Stitches said the guy in charge is working on Prologue but more specifically working on the Gran Turismo TV and just going around the world riding around in his dream cars for that.