It's not really important how 8k will be, the fact is that current pimax 4k version supports only 2k because of hdmi that is not able to transmit higher resolution in 3d with required frequency.
So if you want to find out how the picture from a single eye will looks like all you can do is:
a. set 2k and use lots of supersampling and antialiasing (depending on the game and your g. card) (overall quality is still limited to graphic card/hdmi bandwidth)
b. try to use vorpx and put the resolution to the max possible (overall quality is still limited to graphic card/hdmi bandwidth)
2. imagine a more clear and brighter picture with more colors (current version has lack of this things because of shutter glas).
3. imagine no ghosting
4. imagine doubled horizontal fov
5. imagine less sde (real pixel that you can see on display, not a software pixel)
conclusion: no matter how you raise the quality (&1 a. or b.) there will be not much difference because you're always limited by hdmi cable that is not able to transmit so much information as you're trying to force. Which is more important, current version has some cons described by &2;3;4;5 - and you can only imagine how good it could be without them:)
therefore i would not try to find out how pimax 8k will looks like, it has way to much changes, even if these chances are not completely removing all the issue but still decreasing them - overall immersion from 8k might be impressive and you shouldn't really be able to see something similar in current 4k hmd.