Should work just fine on Proton, previous-gen Creation Engine games worked fine with Wine and DXVK. A few games even have Linux-exclusive patches to prevent crashing on alt-tab, as well as a few performance improvements under the hood.
It really depends on much more locked down the engine will become with ES6. Fallout 4 was notoriously hard to mod for and the modding community suffered for it.
Of course modding difficulty doesn't translate directly to how well Proton will run it, but I fear it will make it difficult for it to be optimized.
