I dunno about that number. I'm still sticking with theory on Sakurai's ideology being "Quality over Quantity". I especially see this in stages more than anything else. The backgrounds and stage designs are extremely detailed and intricate. It's clear that these levels are given much more thought and time than previous game stages.
I mean,
-Lylat Cruise goes through an entire orbit ending in an epic space fight,
-Castle Siege sends the players along a chronological path through destruction of a castle under siege (thus the name),
-Smashville has been given the "synch with real time" theme,
-Sky World makes you feel like you actually are in heaven from the beautiful artistic civilization in the clouds designed in the background.
I only expect a few more than what we got in Melee. I also think this because even if we get the same number as Melee, it will feel like we got more, because the vast majority of Melee levels are unplayable, and I mean, even on a casual level too. I didn't want to play on Poke Floats or Big Blue when I first saw them, and I still don't.