Ahhh, but I keep forgetting about eye-tracking and foveated-rendering, which probably means my current 4yo computer and 1080 will probably be more than enough to handle 4K per eye - no need for SLI or super cards (and a new computer) until you get to 8K/16K. Actually, with the sweet spot so low on current lenses, I'd think they'd could already be rendering the periphery of each screen at a lower resolution and it wouldn't be noticed other than with a higher FPS (I assume they aren't doing this already?).
You're going to have to wait a few more years for that kind of thing to reach us consumers.