It would be awesome becouse they say steamOS will utialize all the cores on cpus and gpus, which is quite an issue nowadays.
sry, but that is not true. utilizing "all the cores on cpus and gpus" is ALWAYS the programmers job, and not the OS's (every modern OS can "utilize all cores", if not, it's not worth the space it's taking up).
more on topic:
relic will not port to steamOS (at least 99.98% sure, prolly even more than that). a port like that costs loads of money, and you need the expertise for the OS, which Relic probably doesn't have (which would make the port probably cost them about as much as making the game in the first place).
also, i doubt that the steamOS will see any significant market share. people that want a pc in their living room to play at or use as a media center probably already have one (and if they do, they can already have steam on it too, whether it be windows or linux steam). but most people will probably use steam exclusively on their desktop pc. people that want to play on TV likely already have some sort of console or something similar.