This would presumably let x86 windows games run on ARM hardware.
This is almost certainly meant for the next Valve VR headset, but ARM has so much better power efficiency than x86 that a future ARM based Deck would be a huge improvement to battery life.
Also see this tweet:
VR games that have already secretly pushed Android ARM builds onto the Steam Store are ran via Waydroid (androidARM to LinuxARM)
VR games that do not have an ARM build on Steam (windows x86) are being translated/emulated via ProtonARM and FEX
Edit: here’s gamingonlinux coverage of this info, includes some more information
Necro-Bump, but Steam announced this last week, that they’ll unleash the Steam Frame in 2026, which will make use of the FEX efforts they have been working on. This thread is a great read in that context, since there is still shockingly little chatter in consumer corners of the internet about this exciting tech.