I think AirPower was a good lesson. If the new Mac Pro is going to be a thing, I think they will give us a sneak peak on Monday, with an announced ship-time of "Later this year" (which is Apple code for March 2020).
One thing I know for sure (by feeling, not by fact), they are not going to tease a new Mac Pro and then not ship it. The "Pro" press would crucify them, and Apple knows it. Therefore, one of three things is certain:
1) The new Mac Pro will be announced on Monday and is ready to ship
2) The new Mac Pro will be announced on Monday and will ship "later this year"
3) The new Mac Pro is nowhere near ready and will not be announced
I pick door number 2.
These are the only three options Apple has available to them. "Hey, we're going to show you this thing we don't know how to build" and then never ship it isn't even an option.
Not after AirPower. Another failure like that—especially for what amounts to little more than a "PC tower"—would yield way too much negative feedback. In fact, I think it would be crushing.
And, considering this thing has the potential to be the most revolutionary tower design ever
(and with the "failure" of the trash can), I suspect Apple knows they have no wiggle room. They have to get it right!