I think if one day we'll have VR with working eye-tracking, high frame-rates will be a lot less computationally demanding. Even at proper resolutions for VR (like 4K or even 8K).
Your eyes only see sharply at just about 2 degrees. Outside of that it all quickly becomes a blur. You brain does the rest to make you think it's all sharp.
At a 100 degrees FoV at 8K resolution, that's like 88*88 pixels per eye that need the best quality rendering, and that's with 8K resolution (i.e. 7680*4320) .
Outside of those 88*88 pixels, you can increasingly (and quickly) drop resolution, AA, texture resolution, shader quality etc.
This might be a bit of an oversimplification, but I suppose even today's PCs should be able to handle that at at least 60fps.
But good eye-tracking will be key here.
Furthermore, when you quickly look elsewhere by turning your eyes/head, your brain needs a bit of time to adjust and see things sharply and process what you see. Test it yourself by opening a book in a random page and see how much time it takes between reading a word in the middle of the left page and reading a word in the middle of the right page.
How long did it take? Half a second? That's like a week in computer time
So there are possibilities for optimization there as well.