-snip profit margins are far more lucrative in the consumer market.
Not trying to be pedantic here, but margins are almost always higher on higher end equipment. Now, if you're talking net profit numbers, sure. But the margins are necesarily low on consumer product because of the competition. Because Apple figured out the key to high volume sales in consumer markets, even relatively low margins equate to big money. That said, Apple does really well margin-wise in the consumer market comparatively speaking.
I would argue that the Mac Pro has simply left the company focus because of volume of sales and lack of enough customer voices being heard. They hear from iPhone and iPad users all the time because of the volume of users. Without volume of sales/users, the Mac Pro squeaky wheel can never be very loud. Ergo, any refresh can wait.
It's a sticky wicket for them, though. If they do decide to ditch Mac Pro, they will most certainly lose cache with the hollywood crowd not to mention the vast majority of good-sized post houses.
I, for one, am already looking into converting our shop to PC. It won't be a small move. We have 80TB of XSAN space, 12 editing stations and tens of thousands of dollars worth of software. If we do go this way, it'll be in no small part related to Apple's decision with regard to the Mac Pro. But truth is, that'll be little consolation at this point since they ditched Final Cut Server, Xserve RAID and Xserve. Those moves hinted at their desire to get out of the pro/enterprise market. They seem to be more focused on the independent market - which is fine and understandable. I just wish they'd come out and say so.
