I think Apple will definitely release a new Mac Pro.
Sadly, like the iMac Pro, I think it'll be ridiculously expensive and so will not be a success.
Mac Pros to some are 'workstations' designed to take on their powerful PC counterparts in large professional environments and be used in render farms etc, but for many others (like me) a Mac Pro is simply the name of the latest Mac tower.
Just like the G3, G4 and G5 were and up until 2012 the pricing of the Mac Pro reflected this heritage.
If Apple target the next Mac Pro purely as a professional machine, it'll bomb massively IMO.
They need to bring out a Mac Pro that will branch both the semi pro/enthusiast and the professional markets (like the cMP did) and to do that it'd have to be FAR cheaper than the recently announced iMac Pro.
Unless they release a Mac Pro model starting at $2500 they needn't bother at all IMO, as it'll be a lemon - just like the trashcan Mac Pro is.
That's not to say they won't sell any (of course they would), but they wouldn't sell enough and would soon be abandoning the sector again.
The iMac Pro isn't the end of the Mac Pro directly, but it may be indirectly. Due to the iMac Pro's huge price tag, Apple will be forced to artificially inflate the cost of the Mac Pro when it's released.
I can imagine I'll be looking at Hackintoshes in future at this rate, which is something I never thought I'd ever have to consider doing.