TL;DR: Valve launched the Steam Frame VR headset with an Arm-based Snapdragon chip, aiming to run Half-Life: Alyx natively and streamed from PC. The new hardware features a “Frame Verified” status for optimized games, while rumors suggest two upcoming Half-Life titles supporting PC and VR cooperative play.
Steam Frame is going to have a snapdragon processor and will “be a computer”.
So there will be an ARM native Steam client (and Steam OS that may or may not be SteamOS). Just a question on whether that gets a wider release.
But yes. Games themselves will be heavily dependent on FEX.