I recently posted in the VR forum here a side-by-side comparison of the Vive -vs- Samsung Odyssey. I'm lucky enough to have access to all the major HMD players, including the MS hololens and Lenovo offerings. I can tell you that the Samsung Odyssey has better visuals in terms of pixel count, but if that's the primary evolution of the Vive Pro, lots of people are going to be disappointed. You still get the 'screen door' effect with the Odyssey, it's just not as pronounced as it is with the Vive.
I think HTC is really shooting themselves in the foot trying to pass this off as an $800 upgrade for 'just' the headset. For the price, I'll keep my existing Vive and just buy the Samsung Odyssey outright. Then I'll essentially have the Vive Pro plus an additional $400 left over. Keep in mind, Steam has a VR translator for WMR HMDs, so any SteamVR content that you already have can be played with the Samsung Odyssey.
I see the HTC Vive Pro playing out like the iPhone X. People that gotta have it are gonna get it. Everyone else will realize it's not that special compared to existing alternatives, especially from themselves (iPhone 8 and the standard Vive).
I agree with some of the other comments here: Skip the Vive Pro and go with a current gen unit. (I recommend the standard Vive.) Or wait for 2nd Gen HMDs. For my money, I'd pick up an existing HTC Vive, enjoy the hell out of it, and then wait to see how the Pimax plays out. If it's all that and a bag of cookies, I'd sell my HTC Vive and put the money towards the Pimax.