This is where Apple could show some "courage" by taking the spinning hard drives out of the 27" iMac, moving to all flash storage, creating a slightly thicker chassis with usable vents that can actually dissipate heat quickly enough along with creating some sort of compact closed loop liquid cooling setup...OR just give us a new tower called the "Mac" that starts with the Kaby Lake X CPUs and let's us BTO up to, let's say, the 10-Core i9-7900X. Anything 12-core or more ( or go straight to dual CPU Xeons) is reserved for the Mac Pro.
The challenge for Apple is now going to be whether or not they recognize where the market is going (more cores...finally), for better or worse, and give their Pro and Prosumer users the options they crave. Me? I don't NEED a Xeon, but I need more than 4 cores and I need/want PCIe slots to update the GPU and add PCIe cards in the future. My desk is a mess with external Thunderbolt "solutions". I can live just fine 3 slots, one x16 for the GPU, one x8 and one x4 should be sufficient for any video or mass storage interfaces I might want or need.
A Mac Pro should have 5-6 PCIe slots and single or dual CPU options, like the 2006-2012 Mac Pros.
That said, I am fairly psyched about the new X-series...12 cores for $1200.00!!! Wow!!! Last year's Broadwell-E 10-core i7-6950X is $1559.78 at Amazon...exciting times. Thank you AMD Ryzen.