4K monitor owner here as well. It is not worth it to bump the resolution further with DLDSR and having it downscale to your monitor. You are better off using Sharpness and other graphical filters to improve the look of the game at that point. Plenty of tutorials on Youtube to use the Nvidia filters they officially provide by simply hitting ALT+Z in game.

There's other things like G Shade that a lot of people use without getting into trouble but haven't researched it that well.

If anything I really hope they develop a new engine for the game and support things like DLSS that allow them to improve graphics big time without burdening the GPU as much. There are big anouncements coming soon and are investing a boat load of money in servers and upgrades. If an engine upgrade doesn't get announced during this time period then its safe to assume it will never happen.

The current game is a graphical downgrade from 1.0, which itself was released 11 years ago...

The trick that improved the graphics the most for me was the making it sharper, I'd say 33%, and I also like the look at a resolution of 4096 x 2160 or true 4K rather than the main stream "4K" of 3840x2160, this does tax your GPU a tad bit more since its pushing more pixels and not all displays have it as an option IIRC