It's not really buyer's remorse. I'm in a situation where competitive advantage is critical. The next camera body must be 4K video capable. I've skipped other upgrades before without feeling competitively compromised, but our market is getting rather more competitive right now.
Never considered video was the requirement. Not good at it; don't do it. Enjoy it from people that do it well.
As to Erik's comments, yes newer bodies generally will be better laden with features and functionality. Don't expect a D5x with that kind of pixel count though. I suspect potentially a D900/D900x maybe. The D900 at 36-50MP and the D900x at much higher. Though if I had to guess, it is more likely a D820 and a D900. Nikon will view the over 50MP as more a MF replacement type camera rather than a simple extension of existing bodies.
Nikon generally has a mindset and then works within that rather than simply chasing market whims. After years, I was proven right that Nikon really, really, didn't want there to exist a pro level DX Nikon body. The D500 is a camera Nikon did not want to produce. It violated their mindset and is why it took some seven years to appear.