"An Event of Overwhelming Force"  Pope Benedict XVI.

... "if one considers the importance that Saturday has in the Old Testament tradition, based on the account of the creation and on the Decalogue, it is evident that only an event of overwhelming force could cause giving up Saturday and replacing it by the first day of the week."

"For me, the celebration of the Lord's Day, which has distinguished the Christian community from the beginning, is one of the strongest proofs that something extraordinary happened on that day: the discovery of the empty sepulcher and the encounter with the risen Lord."

Source: Jesus of Nazareth Part II: Holy Week — From the Entrance into Jerusalem to the Resurrection. Pope Benedict XVI, Zenit.

So it would seem, that the Pope is telling us what he anticipates will be required to impose Sunday on the faithful Sabbath keeping remnant people.

In the very time in which we live, the Lord has called His people and has given them a message to bear. He has called them to expose the wickedness of the man of sin who has made the Sunday law a distinctive power, who has thought to change times and laws, and to oppress the people of God who stand firmly to honor Him by keeping the only true Sabbath, the Sabbath of creation, as holy unto the Lord. He has called them to bear the sign of God, to exalt the Lord in keeping holy His law; for it is a transcript of His character. No part of the law of God and their covenant obligation to keep that law holy is to lose its binding claims upon all the world. Those who have had the light upon keeping the law of Jehovah are to stand firmly in the faith, and to make that light shine forth in clear, distinct rays. {18MR 33.1}

See: The 3 Angel's Messages