I'm currently invovled in two 4E campaigns, one as a player, currently at epic level, which we will probably finish by the time 5E comes out. The group is thinking of taking up Pathfinder next, which I probably won't stick around for as their playstyle suits powergamers more, which does not appeal to me.
The other campaign I run, currently at mid-heroic, I'm thinking of using the E6 system within it, if not we will probably switch to either Pathfinder and use E6 or take up 5E, given the beauty of flatter math. Whichever system we go to, I imagine there will be an influence of 4E which I will somehow incorporate.
I appreciate all systems for what they offer - and even now, when I incorporate a monster from 4E MMs I look it up in previous editions, and compare stats. And make the necessary adjustments (introducing new powers, adding resistances..etc) if I feel the need to.