By the time it'll be out, nobody will care anymore. They've left it far too late already. I despise Valve for all I'm worth but I loved HL2 + the EPs, to see them just shoving it aside in favour of pseudo-tech demo Portal and L4D.
I mean, if they could churn out a sequel to L4D that nobody wanted after just one year, why can't they just make EP3 already? It's grotesquely unfair to make fans wait so long, even more so to do it without giving out info aside from "No, not this year".