GT5 Prologue - Worth it or Wait?

So I'm on the fence about GT5 Prologue. I tried the HD Concept and liked it. Never was much of a racing simulator fan but I'm interested in trying out a new genre of games, and Gran Turismo has certainly peaked my interest with its realism.

However, is it worth getting Prologue, or should I just wait for GT5 itself? Will there be a price reduction for GT5 for the Prologue owners? Paying $40 for Prologue, and then paying $60 for GT5 seems ridiculous if GT5 includes Prologue's content. Or will the PSN offer an update pack for Prologue to bring it up to speed (pun intended) with GT5? Any info and advice is welcomed.

Thanks!