From what I'm reading here, I'm thinking that Moon Lancer has a point. I think the days of static encounters are coming to an end. The idea, I think, will be for encounters to be chained together so that you might have to deal with what would have been three distinct (or whatever number) encounters previous, either consecutively or all at once.
I know that 3e tried to do that in a number of adventures, but, because there was a pretty fine balance on encounters from ok, to overpowering, it was difficult to do. You couldn't throw three +1 EL encounters at the party all at once without expecting a fatality. I'm thinking that with the emphasis on mixed groups, and even just groups of monsters, you'll see adventures being designed to take advantage of this.
In a typical 3e adventure, you fight mooks in Rooms 1, 2 and 3 and then you fight the boss in room 4. Each encounter is more or less distinct from eachother, at least as the adventure is written. 4e will create scenarios where Rooms 1-4 are actually one encounter, stretched out with new opponents arriving at various times.
Just a thought.