Valve's working on Deadlock, an FPS / MOBA. It's very polished, but in early access right now. Based on what I've seen when I tried playing it, and just what I hear in the gaming sphere, it'll probably be a decade-defining multiplayer game once it's done, like TF2 or CSGO both are.

They definitely coast, but when they do release something, it's always phenomenal. I do wish they'd make more games, though.