I'm not sure if you're serious or not, but I am. Steam has already started to offer non-game applications. If SteamOS gets a large enough installed base and provides a good-enough platform for desktop/couch-side apps other than games then things could get interesting.
Yep. Windows 8 isn't very popular amongst gamers. Also, remember Steam in 2003? It wasn't great, but Valve stuck with it and kept making it iterativly better. Also, nowadays most people can get their day to day functionality out of web apps if need be.
EDIT: Of course, it would help if Valve had someone in charge with a record of success in desktop app platforms. Well http://www.computerandvideogames.com/172835/interviews/creat... fancy that.