Well, that's a big if. The Evangelicals are welcome to study Catholicism and convert, and of course we are happy to cooperate on some social issues with the Evangelicals (or anyone else), but the doctrinal differences are not reconcileable at all. A reconciliation with the Orthodox is, on the other hand, the logic of history and undoubtedly will happen perhaps even in our lifetimes, but more likely in a couple of generations. Yet it is the calendar issue that visibly separates us from the Orthodox (and the Orthodox within themselves). We do not have calendar issues with the Protestants that I am aware of, except certain judaizing factions of them.
The WCC is a bastion of false ecumenism: the notion that all differences between Christians are reconcileable. As a whole, that is a silly and profoundly heretical idea. However, if they sponsor a technical study on an issue such as this and help the Orthodox and the Catholics find common ground, that is quite salutary.
There is no division on the issue of Easter. All Orthodox Churches celebrate Easter on the same day, according to the Old Calendar.
You know, I’ve long had this dream that the reconciliation between East and West will be very straightforward: the Orthodox admit that the Romans are right about the calendar, and the Romans admit that the Orthodox are right about everything else.