GameInformer has made a list of the things they believe will happen in 2011. One of them is that Half-Life 3 will finally be revealed. Now some might think that's only a random guess but GI has had a good relation with Valve, they revealed Portal 2 and Dota 2 for example, or they said, that in 2010 we wouldn't hear anything about the next Half-Life game, before Portal 2 was announced.
Whether this is now true or not is up to you but it's the biggest evidence for the next Half-Life game we've had in a while, since the guys from Valve don't really want to talk about it at the moment.
What's also noteworthy, is that they refer to the sequel as being 'Half-Life 3' instead of 'Episode 3'.
Here's the link to the GI article [http://www.gameinformer.com/b/news/archive/2010/12/31/what-s-ahead-game-informer-s-2011-predictions.aspx].
Whether this is now true or not is up to you but it's the biggest evidence for the next Half-Life game we've had in a while, since the guys from Valve don't really want to talk about it at the moment.
What's also noteworthy, is that they refer to the sequel as being 'Half-Life 3' instead of 'Episode 3'.
Here's the link to the GI article [http://www.gameinformer.com/b/news/archive/2010/12/31/what-s-ahead-game-informer-s-2011-predictions.aspx].