Getting anti-cheat that technically already works enabled on Linux has been a lot of work and Epic still won’t enable it. Piracy protection systems will also be an issue. Most EA games inspect your CPU to see if they like it on startup (I think this is using vmprotect and some non-OS x86 calls but don’t quote me on that). These kinds on anti virtualization checks are really common (not just in games ProctorU and lock down browser do them too). I don’t think valve running an open virtualization layer will be well received by companies and they will probably ban it from running games. MMOs (due to botting) and anything with anticheat will look particularly askance at this. I also suspect Valve won’t want to try hiding the VM signatures as it borders on violating DMCA.

Newer games will probably get ported if a large part of the market buys into ARM.