Verno wrote on Jan 12, 2012, 10:34: They announced DOTA 2 because it has a long and lengthy beta period that requires input from "pro" players in terms of balance and whatnot. L4D1 was a purchased property announced by Turtle Rock.
We don't know what the actual Half-Life team is working on but presumably it's Half-Life 3 given the silence and refusal to comment from Valve. I also doubt there will be an actual third episode anymore, I think they'll just roll it into Half-Life 3 somehow. I'm more interested in seeing what they're doing with the latest iteration of the Source engine more than anything else.
Yup. From a post I made a month ago:
Valve has never been fans of announcing games four years before launch. HL2 was announced in May with a release date of September (which it famously missed by a mile, earning Valve a ton of flack and making them guard in-progress games even more tightly.) Portal 2 was announced in March 2010 with a release date of "2010" (which it also missed.) Episode 1 was announced in February 2006 and released in June. TF2, in its current form, was announced summer 2006 and released October 2007. L4D2 was announced in May and released in November.