It's great that it's optimized for their own software, but I'm not sure the FCPX market alone can sustain sales for a machine like this. Especially when I'd guess the majority of FCPX users are on iMacs or Macbook Pros. I realize they have other apps as well (logic, motion), but they're really going to have to get 3rd party developers on board as well for any sort of longevity.
I would love to see Avid take advantage of the new hardware with Pro Tools, as I'm going to buy this machine primarily for audio production. But, knowing Avid, if it even happens it won't be for a very long time.
That being said, the Mac Pro is still the best option for it among the entire mac line. Big core counts, a huge amount of RAM, and an insanely fast disk I/O is all extremely helpful with large sessions at high sample rates/bit depth and multiple resource hungry plug-ins that run on the Native side. Considering that just a couple of convolution reverb or Ozone plugins can max out a 4-core iMac, it's very welcome to be able to jump up to 6/8 cores. More processing power without the thermal constraints of the rMBP or iMac, runs whisper quiet which is amazing for keeping in the same tracking room, etc. Sure, the nMP might be primarily geared towards video production, but that doesn't mean it's a bad choice for audio.
I just want the Haswell-EP refresh and I'm good to go. This machine, even barring any upgrades, would last me a long time, and I'd be extremely pleased with it.