Have to ask if this happened before the iMac refresh just 2 weeks ago, or before the Macbook Pro refresh a few months back that there were all these early morning secret meetings and gigabytes of downloads...if not, then it's something other than just the refresh of the Air or Mac Mini.
Couldn't be the upgrade to Final Cut X either, too niche of a market to get every Apple store buzzing.
One of the few things, logically, that would get everyone in a tizzy and get "training" for store employees and reams of downloads would be something that isn't "shipped", but something that's "announced" and goes live. So my guess would be a Mobile Me revamp.
But then again, that would warrant a live press even from Apple, and has that been scheduled?