I disagree on clearing inventory. They added a couple processor skus. Do you really think they just keep a supply of logic boards and other parts for the next year of sales on hand?
The "inventory" may be the manufacturing production line for the MacPro cheese grater case, power supply, and every thing but the cpus. They may not assemble those on demand, at least the case/power supply.
To the "desktop" sales rate poster: that counts iMacs and Mini's, I believe; would like to see just MacPro broken out.
If there is demand for USB3 and Thunderbolt, someone like Sonnet should just make a PCIe card for that; I can live without it.
I'm guessing that the rumored 2013 MacPro will be a redesign to be more modular. I can easily envision a racking type system into which you plug modules - cpu, memory, graphics, etc.
In the pro-audio world, the API Lunchbox (and even better, the Radial Workhorse) are doing exceedingly well. Basically a 6 to 10 slot (depending on what you want) rack unit into which you plug mic preamps, equalizers, compressors, whatever into a standardized back plane. The back of the unit has all the expected interfaces - audio, etc. outputs. The units automatically talk to each other, etc. Pretty cool.
So I could easily see a similar vertical or horizontal package with modules to plug to achieve the Pro computer you want; upgrades would be replacing a module. Back side would have T-bolt, USB 2/4, Firewire, and maybe others exposed for external connections.
But that's just all speculation.