Unfortunately, Valve would also have to build a CPU translation layer (Like Rosetta 2) since games run on x86 architectures and snapdragon uses an ARM architecture. The steam deck uses a Zen 2 CPU architecture which is already x86 so there would be little motivation on their part to do this. Currently proton uses wine to convert windows api calls into linux calls. The big thing Proton does is allowing games that use DirectX to run on Vulkan which is natively supported in Linux. So unless Valve makes the Steam Deck 2 with ARM or another company decides to make an x86 to ARM translation layer, then I don't see something like Proton coming to android any time soon.