I don't see the Roman Pope ever ceding power to the Constantinople Archpatriarch. There is too much power in the Catholic church to be ceded to the Easterners.A great question: Now that the political class system has been corrected, can Christians reunite?
What does reunite mean? Under the same church?
One of Christ's final prayers was that he prayed that his followers would remain as one, just as he and the Father are one.
Reunification would take time and effort. Everyone would have to begin by taking very small steps and with the realization that each small step is likely to take decades. The first small step would be for each denomination to want to reunite with the denomination it is closest to. For example, Catholics and Orthodox. These two denominations are so close as to be almost indistinguishable, yet our differences continue to separate us. Both call for Christian unity, yet are still one of the best examples of schism within Christianity.
While Catholics and Orthodox are working towards unity, so might other denominations seek out the denomination that is closest to their teachings and philosophies and work towards unity as well.