http://gamingbolt.com/2010/07/22/half-life-2-episode-3-found-in-the-alien-swarm-sdk/

Half Life 2: Episode 3 found in the Alien Swarm SDK!

July 22nd, 2010 at 7:54 am-

Over at the Steam Forums, a user by the name StickZero has apparently found something really very interesting. He’s found some assets in the Alien Swarm SDK that points towards growing evidence that Half Life 2: Episode 3 is in development. If you open the Alien Swarm SDK, place an info_node_hint and check the hint options you will see Aperture Nest, Blob Brain etc. This is definitely a proof that Valve has already started working on the game. But again, take this with a pinch of salt. Check the image below, courtesy dl.dropbox.com.

Click the image to see it in full screen:

They better bloody be developing it!

Was there ever any doubt that they're developing Episode 3? They can't very well leave it hanging. The only question is when does it come out?

Well of course it's in development - it's already late on initial estimates so it'd be a bit worrying if it wasn't.  Only question is why are bits of it in the SDK?

I think we can assume ep3 has been in development since the launch of ep2 at the latest, I wonder whether they will use it to launch source engine 2.0

Pretty sweet.

Maybe it's a lot longer than Ep 1 and 2? Or maybe they just taking time to make sure the ending is unforgettable.

How long is HL2 and Ep1 and Ep2 resepctively? Ive asked this before but i foergot.

They are both about 2-4 hours long depending on level of difficulty etc and pace of the player.

they better be i have waited long enough and it better look mile better than ep 2