Steffen Dunner has been doing some tests with the Texture Caching branch from Stefan Werner, and he did a test with a ton of 8k textures, I have to say that the results are incredible:
Here is the branch in case it's useful:
https://git.blender.org/gitweb/gitweb.c ... ture_cache
This would be amazing, just with this the amount of memory taken by textures in general could be reduced A LOT and that would make 8Gb GPU's much more viable to render serious projects
