When the Apple store came back online after the show, a "New" tag on the Mac Pro hinted at a stealth update. Glancing over the specs for the supposedly new system turned up only a clock speed bump to a few of the available Xeon processors.
Rather than the quad-core, 2.8GHz Intel Xeon W3530 chip, for example, now the $2,499 Mac Pro starts with a 3.2GHz quad Xeon W3565, a chip using the same Bloomfield core architecture that Intel debuted in 2008.
Otherwise, the Mac Pro appears unchanged. The graphics cards, memory, and hard-drive options remain the same as before. Apple has also not added Thunderbolt, or even USB 3.0 (which makes sense, given the older Mac Pro motherboard chipsets).
Why the minor CPU update? Tech Crunch's John Biggs, who first noticed the CPU update, suggests it's for Mountain Lion compatibility. Apple says Mountain Lion will work with Mac Pros dating back to 2008, though. Perhaps the CPU update is targeting one particular Mountain Lion feature, but none of them looks particularly processor intensive.
Regardless of the reason, this is indeed a minor update to the Mac Pro, and to the desktop in general. Ivy Bridge and USB 3.0 are still absent among all of the wired Macs. A Retina Display update on the iMac might also have been nice.
An update to the Mac desktop line could happen at any time, of course. Between its updated MacBook Air and MacBook Pros (new and old), and new announcements for Mountain Lion and iOS 6, the company had no trouble filling out 2 hours of presentation time. It didn't have time to mention the updated AirPort Express wireless router (finally, simultaneous dual-band 802.11n!).
I'm willing to bet we'll see an updated iMac at least before the end of the year. I'd even go so far as to say I think we'll see Ivy Bridge comes to Apple's all-in-one before Apple introduces the iPhone 5. If you've been holding off on an iMac purchase in anticipation of an update today, my advice is that you stay patient.