However some are speculating that by 2012 Apple will be dropping the Mac Pro.
I'm one of them, but think 2013 will be the last year, given the direction Intel's moving with the Xeon parts. More cores, and higher prices. Too many and too high a processor cost to continue to use them in workstations, so no one would be able to afford them.
Desktop parts are an option to continue the line, but then there's a collision with the iMac's marketing strategy and sales figures. Separation would be more financial than parts (save core counts, as the high-end desktop parts will have 8 cores on a single die - derived from the next Tock cycle Xeon).
I think that Apple have spread themselves so wide that they can't give the pro market the attention it needs. The consumer side has gotten so huge it doesn't make sense due to every diminishing returns.
The bulk of their revenue is in the consumer lines, so that gets the bulk of the attention as a result.
As far as Apple giving up the professional market, it makes no sense.
I do, and see it as financially motivated.
Intel's shifting the focus of the Xeon line to suit enterprise's desire for cloud based computing. So the core count will be higher than is needed for a workstation, as will the price. Combine it with a small market share, and it doesn't look good IMO. Users wouldn't be able/willing to purchase the systems at some point (2014 IMO, so the last is likely 2013), reducing the sales to the point where such a product would be a financial loss if proceeded with.
Now they can go with high end desktop parts at that point, but I'm not sure they will, given the potential impact on iMac sales, and a small market to begin with. Again, the price would likely be too much for the market to bear. It's possible, but I'm not sure they're going to go that route. I just don't see 8 core + desktop parts as being most people's idea of inexpensive, especially when Apple's idea of profit margin is added.
But in general, that's where I see the workstation going, as there won't be a choice given Intel's CPU offerings at that time (end of the Xeon based workstation).