Not a defense, but I am guessing they are waiting for the next set of Xeon processors on Intel's roadmap. I understand Intel has announced 2018 Q1 for a group of processors.
Not only that, but I think that Apple is feeling the Pro user backlash and are really trying hard to say "sorry, but there is something awesome in the pipeline" where the pipeline is a few months old at most.
It takes a while to get a product to market and this would seem to answer most of the criticism the pro market has had with the mac pro so far, the macbook pro is a different beast.
Apple has weathered, and thrived during, much worse "backlashes" than the current one, which is itself lacking any evidence of being a real thing in terms of Apple's bottom line. AAPL is up over 50% since I bought it last year when everyone was claiming the iPhone was over.
Also I imagine graphic card makers - it was a shame to see microsoft products with Nvidia 9xx series when 10xx is huge step up in performance/energy effectiveness. Plus something with storage - new intel optane would be nice for pro machine and so on.
