L4D2 is an extraordinarily good game, and Valve is an amazing company - the closest cultural fit I can imagine to Linux, for a company that (of course) sells proprietary software and uses DRM. Most of Valve's other games are recognised leaders too (e.g. Half-Life reinvented the first person shooter) and they already support Mac to some degree.
Not sure whether this will mean Linux getting a lot of Windows games, but it's a good start, and a Linux-based Steam console would be great.
PC games (i.e. Windows/Mac currently) are much more open to modding (extensions, new maps, etc) than console games, so there's hope that a Steam console would be more open and PC-like (above the Linux core) than the Xbox/PS3/Wii.