I'm speculating that there will be a major update to the Source/Orange Engine for modders, or they are going to release an HL3/CS:S2.
This is what i would like. A HL3/CS2 combo. Say what you like about CS when it was 1st released (pre source) i played it.. a lot. It was a truly great game when you had a team of people all on comms using tactics to plant or defend a bomb. I accept that when CS:Source came along it became tiresome. My pet hate is the overwhelming amount of servers that play Dust 2 constantly. I never liked Dust 2 myself and i missed all the maps that we lost when they switched to CS: Source.