I'm thinking that for 99% of still photographers, the new Mac Pro will be much more expensive than useful. I can work with Photoshop on my 2013 MBP, and while with some very large files, it can slow down, my Windows workstation is not much faster for most photographs. This is a dual processor HP Z820 with 128gb RAM and an Nvidia Titan X GPU with 11gb Vram.
The one advantage of my Windows workstation (I use it for motion picture color correction) is that is has 128Gb of RAM. And that means with very large files, it does not need to use a disk cache which speeds work with large files. To my surprise though, the workstation also takes a long time to save large files, even to high speed media or even the RAID.
If you're doing video, and desire a Mac, then I can see investing in the new Mac Pro. Maybe also if you're working with very large files, such as panoramas and stitching. Or, maybe just scrolling through hundreds of images at a time in LightRoom. For the average landscape photographer... Maybe a nice iMac is a much better buy.