Eh, I could tell that this was a request thread. Honestly, I'd rather have 3 - 5 smaller tracks in Prologue than the Nurb. I can wait for the track of glory in the real deal. Oh, and a few race cars too which are similar in performance so no one car dominates.
I could see this happening in an update to Prologue if GT5 slips into 2010, that we'd get more cars, tracks, a few more tuning options and some of GT5's online features to tide us over. And it may still happen if GT5 won't show until December worldwide, to keep us juiced and boost a few more sales of Prologue. We'll see in a little over a week.
Man, time is crawling...