I don't mind a L4D2, the new Director additions sound awesome. The Charger replacement for the tank is stupid though, yet Coach is awesome because he's like Uncle Phil :D
They aren't replacing any special infected, they are adding a Charger and a Spitter. Tank stays. I have no worries about L4D2 other than the characters, I can only hope they are awesome as the first 4. The video talks about them a little and they look pretty cool though.
Also, I'd love a Portal2 but I have no clue how they would ever add to the story, it's kind of a finished story. CS2 sounds handicapped, you can't add any benefits to such a game other than graphics or new weapons, and the weapons and stuff could be added with an update.