Yes, I think Steam OS gamers will use Steam OS to emulate games from other consoles like Playstation because Steam OS is based on Linux, so Emulators made for Linux, and Android which is based on Linux will most likely work on Steam OS.
I think all Alternative consoles like Ouya, Steam box, Gamestick, iConsole, etc will have people using their consoles for emulators since they all run on either Android, and Linux which are Open, so people can use them for whatever they want.
Tell me when an emulator becomes available for Steam. Then, it'll happen. However, SteamOS itself needs Steam support for the game/application, so we need to remember that as a limit.
I read Steam OS uses a modified version of Ubuntu 12.04 LTS, so sideloading an Emulator like ePSXe and pSX. which works on Ubuntu Linux onto Steam OS should not be as hard for tech savvy gamers if Steam OS does not lock down the root account, terminal, or sudo.