I can say that I made wrong decision when decide to stay with X99.
Everything works fine and my watercooling parts arrive soon but I could bought i7-7820X instead
upgrade RVE motherboard and sell CPU and motherboard in that time and use EVGA X299 Dark.
Only she was not available in that moment.
Motherboard is problem, because I used on models from high class, Skylake-X I will find cheaper than Broadwell-E.
Now I would have X299 Dark + i7-7820X 8 cores and Supremacy EVO CPU waterblock, EKWB XRES D5 Revo 100 Glass, I ordered.
Skylake-X not OC as X99, but far better than AMD and work on 4.7GHz and that's insane speed for 8 cores and impression in games much better than 4.0GHz CPU with 1000 Cores.
I would not worry about Cascade Lake or future of X299. More to upgrade from i7-7820X to i9-7920X or similar later.
With so good motherboard she force you to stay on that some platform longer time and X299 Dark is really unusuall.
Like some Anniversary board or similar.