Forget Half-Life, there's not going to be a new one any time soon. I think Marc Laidlaw's recent comments show that although he would like there to be another game he doesn't have enough support from the rest of the company to actually make it happen.
While making cryptic comments about secret Valve news is an incredibly cheap (and easy) way to generate page hits, people really should have learned by now that it's never going to be anything to do with a new installment of a Valve game unless Valve themselves say it.
And as for Half-Life...
Gamestop has been doing this for ages. They make up an end-of-quarter release date to convince people to pre-order and just change it when that date passes. Last year it was 31/12/2012, now it's 30/06/2013.
In 3 months' time they'll change it to 31/12/2013.
Source 2 is in development yes, that's news. But all he said was that they are waiting for "a game" and you've just assumed Half-Life 3 because of past history with their engines.
But I'm not interested in them. I only have time for single-player games these days and Counter-Strike and Dota...