I think it would be good to begin by looking at what the Saints, Fathers, Doctors and other theologians and authorities have said about such a situation.
But anyway, Telesphorus, about 10 days before the consecrations, reflecting on why the discussions with the Roman authorities had failed, the Archbishop said the situation was no more about a "pure and simple" canonical recognition of the Society.
Archbishop Lefebvre said he had mentioned at the beginning two conditions in particular "bishops taken from within Tradition" and "majority on the Roman commission" to be "well protected from liberal influences". So he envisioned a situation where post-regularization sufficient protection for Tradition would be granted, enabling the Society to work toward the restoration of Tradition to Rome and the mainstream Church.
There are several other statements he made both slightly before and after 1988 to this effect. The Society has now added to that almost 7 conditions, 3 preconditions already granted, 3 sine qua non conditions which are individually necessary and collectively sufficient for the protection of Tradition post regularization if at all it happens, 3 desirable conditions which if granted will hasten the return of Tradition to Rome.
So, by that same standard, especially considering two important developments in particular since 1988, the fact that every priest's right to say the traditional Mass has been juridically recognized, second, that especially following the doctrinal discussions, some of Rome's own professors and other persons in positions of authority, I'm not talking only about Romano Amerio and Brunero Gherardini, in the mainstream Church have begun to question and criticize the Conciliar texts themselves like never before, see the DICI articles on this subject, Bishop Fellay and the other Bishops and priests reason, that a no strings or in the Archbishop's words a "pure and simple" canonical regularization under the right sine qua non conditions granted in advance is something good and not to be refused if it is offered.