A GameSlice podcast (AOL no longer required) features Valve's Gabe Newell and Erik Johnson chatting with Geoff Keighley about various topics. Those of you who remember your parents talking about Half-Life may be interested in the discussion of the series that's reported on IGN (thanks nin), where they note Gabe Newell saying "I get it," when it comes to user frustrations at their refusal to conclude the series, adding: "I certainly understand why people are like, 'hey, I remember this awesome experience, and I'm starting to get worried that I'm never going to get to have it again'." The sanguine conclusion he draws after that suggests either they will actually remedy this situation, or that he doesn't get it at all, as he says: "So we understand it and we feel that, and we think at the end of the day, customers are going to be really happy with where we spent our time and how we've turned that into entertainment for them." Whatever it is he does get about this, his comments don't suggest we're going to get a new Half-Life game anytime soon, though this overview suggests that if this does happen, multiplayer will no longer be an afterthought:

But we are also going to build on what we learned, and we have learned a lot. We aren’t going to go all retro because there are too many interesting things that have been learned. The only reason we would go back and do like a ‘super classic’ kind of product is if a whole bunch of people internally at Valve said they wanted to do it, and had a reasonable explanation for why it was. But, you know, if you wanted to do another Half-Life game and you want to ignore everything we have learned in shipping Portal 2, and in shipping all the updates on the multiplayer side, that seems like a bad choice. So we will keep moving forward but that doesn’t necessarily always mean what people are worried that it might mean."