It depends on how the program works. If SteamOS works like Android then yeah we might be cooked on the hardware support. If SteamOS works like a normal linux distro/OS we'll get more support.
In practice this is a good thing because most of the parts of SteamOS are open source, meaning that as long as you don't have a device with a locked bootloader you'd be able to run comparable OS simply using all the software that's bundled in Steam OS.
"they're only prisoners of war if they're taken by governments recognized in the United Nations region, otherwise they're sparkling hostages" - US Department of State