Fine with 1080 but should I still get 4k for the e

I don't quite get the idea of "default to 4K and logically downgrade" lower. If you mean that GPUs will one day be so advanced the lower tier would run 4K monitors with ease, I'm not sure we'll necessarily see that. Testing has shown pretty strongly that the better experience in gaming is had from higher framerates, and not so much from higher resolution. The combination of both is very expensive to buy. I think the marketplace will always have room for GPUs that deliver high fps at lower resolutions, but also come with better enhancements like ray tracing and DLSS. I think the best strategy is to buy the best GPU you can for the monitor and fps you want to drive, and let future needs be taken care of by upgrading. A newer gen of GPU will always come with features the one you own doesn't have, and that's the path you want to be on.

I'm not sure we're talking about the same thing, but that's my interpretation of the question. A higher pixel count (resolution) matters more the larger the monitor.