Apple still only uses Moscone West (at least as of last year). They could also use Moscone North & South as the big conferences do (Oracle OpenWorld/Dreamforce/etc)

The problem is still room sizes. You would almost need to mirror the conference in each venue. The Apple engineer area/cafeteria etc. couldn't really hold any more.

Moscone North alone would be an improvement from Moscone West. Heck, just take over all of Moscone for the week!

I've been told the reason the event has been kept small is to maintain the same ratio of Apple developers to attendees. But I think that overstates the value of the Apple devs a bit. The attendees at this event really are one of a kind.

They haven't done the traditional post-session question & answer time in years, so other than the "labs", there is no interaction with the Apple engineers. They could set up a more stringent reservation system for the labs and sell more conference tickets if they wanted.

But, like another poster said, selling out in under 2 minutes makes them look good.