...I can pretty much guarantee it will not be about the PvP.
CoX has NEVER been about the PvP. Infamously so. They recently updated the PvP and alienated the majority of their dedicated PvP'ers an attempt to get the PvE crowd involved.
No, this will be the long-awaited "crossover"; Brutes, Dominators, Stalkers, Corruptors and Masterminds will roam the streets of Paragon, not as enemies, but as heroes themselves! Personally, I can't wait. Also, the chance for Villains to enjoy the benefits of a real tank can never be underestimated. It effectively doubles the size of both games.
Of course, with my luck, I won't be able to afford the subscription for both CoH AND CO by that point.