The Pope’s long-rumored Apostolic Letter issued motu proprio (“on his own motion”) facilitating the use of the classical Roman liturgy is now out, along with an explanatory letter from the Pope addressed to the world’s bishops. I’ve commented already on why I think the issue is important and the Motu Proprio has world-historical importance, so I won’t repeat myself.
A quick reading suggests that the Pope has been intelligent and thorough at all levels. The essential reason for the move is the Pope’s “hermeneutic of continuity”: the Catholic Church is the same Church before and after Vatican II. Consequently, the Roman liturgy, the supreme embodiment of the faith of the Church, must also be viewed as the same liturgy before and after the reform. The new cannot reject or devalue the old. The pronouncement therefore treats the Old and New Mass simply as different forms of the Latin Rite, both of which are legitimate and permitted, and calls on clergy and bishops to accommodate in some rather specific ways those who prefer the former. If they don’t cooperate then it’s the job of the Ecclesia Dei commision in Rome to see what can be done.
My guess is that if a particular bishop really wants to suppress the Tridentine Mass in his diocese he’ll mostly be able to do so one way or another. The Pope evidently wants the Tridentine Mass to be accepted as part of the normal local functioning of the Church, and to affect the understanding, presentation and development of the New Mass, and that means he can’t ride altogether roughshod over local authorities. You can’t impose a more organic liturgy by decree from Rome. Still, the letters radically change the setting in which such issues play out, and as the Vatican II generation continues to retire or die out I think we’ll see less episcopal intransigence on the point.