For what little it's worth, I expect 4e to enter the "Mearls Transitional Stage" in about a year - you know, much like how Mearls shook up 3.5 when he joined the team, with books piloting 4e mechanics (PHB2, Bo9S, Complete Mage, Complete Champion, etc.)
Whether this will herald a 5e, or a separate branch of 4e, remains to be seen.
I've said all along, "They are not making a new edition until they start hiring." If you hire someone as high-profile as Monte Cook, you're cooking up something big. I don't know what - other than a new edition or major branching of the 4e core - that could indicate.
However, I'm a happy 4e player and subscriber. I don't care what will come out in a few years - I'm running a game now, and loving 4e, and DDI is very much worth the money.
-O