On the topic. A rare but vague answer on this subject from Mateusz Tomaszkiewicz of CDPR which indicates "some interest" in supporting SteamOS (which means Linux support in essence):
Q: Hi. I was just curios what CD Projekt Red's position on SteamOS and Steambox is? Does it interest you, or it's just an extra road(?) on the ladder(?) of platforms you support?
A: I think it's more of a question to my superiors to be honest, but... hehe. I know that it's not out of the question. I know that there is some interest in it, but as I said, it's not, you know, kind of decision that I could make or even be included into.