The sacking of Constantinople has opened the doors for Ottoman expansion into Europe. One has only to read open support Vatican offers to the Islamist expansion into Europe in the 1990s to find out that RC church has not learned anything from the past - Vatican dreams of destruction of Orthodox Christianity, even if such destruction will bring down Europe.
In general, however the Italians outside of the vatican get along fine with the Orthodox Russkies and visit Alexy from time to time. They have told Alexy they think the pope is out of line.
So there may be hope from Italy.