Apple has as much interest in the Mac Pro as any other mac. Once Apple committed to thunderbolt, the cMP days were numbered. You can't implement thunderbolt on generic video cards. No matter what form factor the nMP came in, it was going to have custom video cards.
On the technical side, There hasn't been a compelling reason to update it since the current model came out at the end of 2013. Haswell-EP has only slight speed increases compared to Ivy Bridge-EP. On the GPU side, AMD came out with the 290X (hawaii), but that GPU is very hot, and likely would have thermal and power constraints. NVIDIA's 900 series (Maxwell) is a great gaming GPU, and I expect we will see that in a mac somewhere, but probably not the mac pro. Apple likes to use AMD because they tend to be better for compute workloads, and AMD is much more willing to make custom designs than NVIDIA.
Besides, 1.5 - 2 years has always been standard for the mac pro. Updates to these higher end components just don't happen as often as other consumer parts. Not to mention that the last couple years has seen progress stagnate in trying to shrink down the transistor size.
I wouldn't be surprised to see a new mac pro at WWDC. Apple could throw in new Haswell-EP processors from intel and new GPUs (Fiji) from AMD in there. Although, I think the only way it warrants stage time in a keynote is if they can get thunderbolt 3 on it and introduce a thunderbolt retina display.
Unfortunately the rumors regarding macs have become more sparse. The fun part about iPhones and watches stealing the Apple rumor limelight is that now the mac releases are a bit more secretive.