I find it much more likely that Valve enables Secure Boot on their Steam hardware.
I imagine that if this happens, it will be followed by popular Linux distros finally becoming serious about their Secure Boot implementations, instead of simply shimming it or seen as a rarely-used feature reserved for enterprise distros like RHEL.
Some of us actually think that having some sort of validation that our OS hasn't been tampered with is a feature and not a bug. It's only a problem when companies parlay that validation into anti-consumer DRM - but that's a political problem, not a technological one.