Last night I was reading and it appears that Valve thinks that if they release HL3 that it will affect the sales on other games across the board. At least that was one of the reasons. And that their focus is more on the community aspect of Steam. Using their resources to improve game experience as a whole instead of creating a new game. Plus you can go to Gabe's Twitter account and if I were a betting man from his responses, I just don't see them making it a priority anytime soon.
If you think about it, it kind of makes sense. Because the game would not be focused on multiplayer. Unless you do a HL3 Deathmatch which I am sure they would. But would players jump on board to play deathmatch again for Half-Life?
I dont know, I have mixed thoughts about the whole thing anyways. I did hear that the main character, if it were made, would not be Gordon so much as it wold be G-Man.
If they were smart, they would come out with a TF3.