I've found my favorite level in the game, methinks.
But, I don't think this game is only going to have eight levels by a long shot. More like multiple acts per zone, I think. I mean really - that trailer is really darn schizo - about half of it is on an ocean/lagoon, while the other is in what looks like a desert/jungle canyon. Unless the level really is that dang huge, this has to be multiple zones. Besides, keep in mind how much we knew about SSR by the time it came out. IIRC, we had seen everything except ... what, Skeleton Dome, Night Palace, and Lost Prologue.
Oh, and somebody REALLY messed up the sound effects on that. Possibly stating the obvious, but they accidentally used the lose ring effect for gaining rings.
EDIT:
Oh yeah, just realized this too. The first Spagonia video featured what looked like a boss fight; yet there's video of the entire Spagonia level (Wii version) on YouTube from TGS. No bosses there. While it's possible that the boss locations have differed between the 360 and Wii versions, I think it hints more to there being multiple parts to each area - maybe Secret Rings style?