There are many 'chinese whispers' circulating throughout the competative counter strike scene atm: Through talking to different top level Counter Strike Source players and figures, it has become apparent that Valve has sent out a string of invites to travel to the Seattle headquarters. Many of the players are reluctant to speak publically about them, but many have accidentally admitted being invited.
This would hint at a new Counter Strike. Usually a new Counter Strike means a new game engine. This would tie in nicely with TF2 being made free.
The rumor is Valve is working on the next groundbreaking engine since Source. This would mean new TF/CS/HL
The world's a changin if this be true.