With faster links downloading and uploading is not a problem (I have 100/40Mbps unlimited data, in Europe 300/300Mbps is available, in the US even higher). Storage is also cheap.. $50 / TB here.. much less in the US.
I already have some UHD/4K porn, mainly Helix. It is great to watch but sometimes too much resolution and detail is not good. Every ingrown hair and blemish is visible.
A bit like 3D porn.. I kept getting distracted from the 'action' by what was in the distance and the surrounds.
You'll find that most porn is now shot in 4K then edited and downsized to suit the delivery system (DVD, BluRay, download, streaming… whatever).