As much as I dislike the externalization of all my components, I can agree with Doug that the Mac Pro 2013 has served me really well. I got a 6 core version with the base storage and ram, and then upgraded ram to 64gb via OWC. Since then it has done very well as a reliable, efficient computer. Now that I am editing more 4k video, however, I have found render times to be a bit annoying, particularly for things like H265 and noise reduction. Additionally, Lightroom can lag quite a bit when spotting large images and film scans, though I mostly do that in Photoshop anyway, as it is faster and better.
I am looking forward to the new Mac Pro, but the price is daunting. I am curious to see how much you actually get at the entry level...6000 dollars for a computer with a 256gb hard drive is pretty tough to swallow. I know that most that consider this computer use external storage, myself included, but having more space with that extremely fast storage can be extremely useful for apps, transferring data and so on.
Overall, however, it seems like I will still need some sort of dock or set of adapters with the new Mac Pro, as it does not have a firewire port for my scanner (unsurprisingly), thunderbolt for my monitor, or enough USB ports for all the various USB 2 and 3 things like my printer, card readers, keyboard, mouse (for charging), phone, external drives for clients etc. I do not really object to them making most things USB-C, but compared to what it was like with a Mac Pro in the mid 2000s, it still seems like you will need a bunch of external bits and bobs to keep it organized. As far as I recall from the G5 and pre-trash can era, nearly everything could plug in natively and with 4 bays it was enough most people's needs. Times, of course, change.
P.S. There is also the elephant in the room regarding the new OS versions...I keep getting messages all the time about how "this software needs to be updated by its developer", so all the 32 bit apps will stop working. I think that will mean we will be out of luck running FlexColor on the new MacPro. That would be the biggest hit for me. Other things like i1 profiler will likely update themselves if they haven't already.