A core doctrine of the Catholic Church is that the pope rules over the entire Church with absolute, immediate, universal jurisdiction. This isn't changing, not now, not ever. In Catholic doctrine, there is not and cannot ever be any such thing as an autocephalous church because:
- "absolute" means there is no aspect of church governance, liturgy, and teaching over which the pope lacks authority. If the Orthodox Churches were to enter communion with Rome, they would have to agree that their patriarchates and rites exist because the pope chooses to allow them to exist, for as long as he chooses to do so, and that he may change or abolish them as he chooses.
- "immediate" means that the pope may, if he chooses, bypass the hierarchy entirely and issue orders to an individual parish or even layman; i.e., he has no obligation to gain approval from any council, patriarch, bishop, abbot, or clergy. For example, if the Russian Orthodox church were to join the Catholic Church in communion, it agrees that the pope has the right, if he so chooses, to direct an individual parish in Russia to send its icons to Rome. He may call a priest in Novosibirsk to the Vatican, or reassign him to India. He may order a parish in some random Siberian shithole to paint its walls magenta with green stripes. Any order he chooses to issue, no patriarch or bishop has the right to countermand.
- "universal" means there can be no partition of the Church which is not fully submitted to the pope's authority. Autocephaly is not just disobedient, it is heretical. That is, not only would each of the Orthodox Churches agree that the pope has absolute, immediate jurisdiction over their churches, it would also have to agree that the very notion of a church over which the pope lacks such jurisdiction is a heresy, contradicting the voice of the Holy Spirit that spoke through the Church at the Vatican Council.
Additionally, the Orthodox Church must also agree that councils derive their authority from the pope, and that a council is "ecumenical" if and only if it is authorized and validated by the pope. This is a doctrine of the Church formally stated at Vatican I. Trent, Vatican I, and Vatican II are ecumenical councils, because the pope says they are, and the Orthodox Churches must agree to this for full communion with Rome. There is Z E R O chance that the Orthodox Church as a whole agrees to any of this.