On modern cards the resolution isn’t really the limiting factor, nor is it just about monitors anymore.
On VR Oculus Rift / Vive resolutions that people run today:
PD 1.0 @ 2160x1200 resolution = 2,592,000 pixels
PD 1.5 @ 3240x1800 resolution = 5,832,000 pixels
PD 2.0 @ 4320x2400 resolution = 10,368,000 pixels
PD 2.5 @ 5400x3000 resolution = 16,200,000 pixels
Examples of PD in use: Pixel Density Examples - Meta Community Forums - 632152
Even without VR, for years I ran 3 plain monitors, which was:
1920x1080 x 3 @ 5760x1080 resolution = 6,220,800 pixels
Beyond the Gen 1.0 version of VR, it’ll get a lot higher:
Vive Pro / Samsung : PD 1.0 @ 2,880x1600 = 4,608,000 pixels
Vive Pro / Samsung : PD 2.0 @ 5,760x3200 = 18,432,000 pixels
With next up Gen 2.0 coming (maybe, Pimax 5k is at least meant to release in the next couple of months):
Pimax 8k: PD 1.0 : 2 x 3,840x2,160 = 16,588,800 pixels
Rift 2 / Vive 2 - who knows, but probably not lower?
The thing is not really to think about pure amount of pixels in VR, as they aren’t evenly distributed because of how the lenses work - the density is higher in the center as the lens warps the view. Also, the best next steps approach beyond the 8k would be things like foveated rendering, which dynamically make the images sharper where your eye is looking directly, rather than ‘waste’ pixels in your peripheral vision. That might allow a very different VR experience using similar (1080ti ish) cards with 8K like views.
Pixel fill rates are getting faster, but GPUs do a lot more than that nowadays, including vector and geometry work that scales hard at O(n) rates, meaning that it’s really diminishing returns.
For future 2D flat displays, the next up Apple OLED based 7,680×4,320 8K monitor rumors look nice. Not cheap though, but great professional refresh rates and solid colors.