Yes parts will be available for some time,
... but it won't matter to most , once they have bought the eventual replacement to the current MacSlows.
You're making no logical sense here. No real explaination or support.
Because of NAB...
Mac Pro
April NAB Release: WAY more sales.
May/June Release: Average to less sales.
The MP is a niche product, and those that need one, do their research. That is, they pay very close attention to any information that's released (leaks, official announcements; including Intel,...). So it's much more immune/insulated than consumer products in terms of release dates & sales. People will wait if at all possible, otherwise if its immediate need, they'll buy what's currently available, as it's earning an income.
What about this? If Apple decides it can't profit from making its own Mac Pros, might it do a limited licensing program for another company or two to make high-end clones? Unlike their clone program in the 90s, they could choose to limit the licenses to specific high-end models that did not compete with iMacs or MacBooks. And they could include an Apple certification process so that quality and stability would be maintained. Really just a form of subcontracting, but possibly co-branded with the actual manufacturer (I dunno, HP or somebody like that). Seems like it could be a win-win-win: Apple wins from license revenues without undercutting its own profitable lines; partner company wins from hardware profits; users win by having a motivated producer of up-to-date hardware.
Or is this simply such a non-Steve thing that it just can't happen?
As it stands, the MP is already contracted out to ODM's. They don't touch the software side however.
What you propose isn't likely at all, given their penchant for secrecy, and most importantly, absolute control. Licensing OS X while other systems they sell still uses it (full OS X, not the device variant/s), would sacrifice control.
My earlier comments on licensing is based on the premise that Apple ends everything but the portable device market (nothing that runs full OS X any longer). This would put them in a position that they essentially have to, as they'd no longer produce (sell, as the hardware is ODM'ed save the enclosure) a system that they can use as a developer platform.
They may have been released but the 5600 series 6 core Xeons are in very short supply at the moment.
I'm not sure if they're having slow start issues with the 32nm process, or are holding parts for large volume contracts in order to meet delivery deadlines set within them.
But getting your hands on one via the retail channels isn't that easy yet.
Provantage has them in stock, so if resellers have them, you can bet your bottom dollar that Apple does (or can).
Provantage 6-Core Xeons
I took a look, and they had 1 part in stock (Q = 1) of a Retail X5670. Everything else was listed as special order/out of stock.
They could be storing/stockpiling parts for an order made by Apple (and other vendors) to meet the negotiated delivery date & quantity schedule (parts are shipped over time, so it's not one massive delivery).