I answered this question a while back in a post started years ago started by Matthew that contained a number of questions for sedevacantists. To answer your question, first I must say that I don't speak for other sedevacantists nor do they speak for me.
How will the crisis end? I don't know.
I do have a few ideas about how it might end, however.
As the realisation that the See of Rome is vacant began to solidify, some Church theologians began to try to develop theological theories based on the writings of popes and theolgians of the past (most notably Saint Robert Bellarmine and others) as to how the crisis was possible. The whole situation seemed to be impossible, yet there it was staring every Catholic in the face.
One theory suggests that the Conciliar Pope is "materially" pope, but not "formally" pope--similar to the material/formal heresy argument. He is filling the chair, so to speak, and has the power to govern secular matters, e.g., appointments, creating and suppressing dioceses, etc; but he has not the power to exercise papal authority (since he is an apostate and a heretic) and therefore cannot rule the Church in matters of faith and morals. If this theory is correct, then we merely have to wait for a Catholic to be elected to the papacy.
This is possible since we, individual sedevacantists, cannot possibly pass judgment on every single person attached to the Conciliar structures. Most of us remember a time when we had the faith but were living in those structures trying to make sense of what was going on. Surely, there are some priests, bishops, and maybe even cardinals that still have the Catholic faith but are simply too spiritually weak at this time to declare it.
Should a Catholic be elected, it will be manifest in this way: First, knowing that the validity of the new rites of ordination and consecration were questioned almost immediately after their promulgation, he will appoint a commission to study the matter. The commission will either find that the new rites are intrinsically invalid or that the new rites are only sometimes valid due to various factors. He will immediately suppress the new rites and the newly elected "pope" will then seek out all of the clearly valid bishops in the world including the Society bishops and some of the Thuc-line bishops and ask them to conditionally ordain and consecrate every Concilliar bishop in the world, including himself, in order to remove all doubts in the minds of the faithful. He will also require all priests to be conditionally ordained.
While he will not immediately supress the Novus Ordo, he, himself, will never say it and his example will cause, in a matter of a few years, render the Novus Ordo obsolete. After a year or two, he will consecrate Russia to the Immaculate Heart of Mary along with all the bishops of the Catholic Church and within a short time, Russia will be converted to the Catholic faith.
The secular press will never have anything good to say about him and he will eliminate all the ecuмenical nonsense calling on non-Catholics to convert to the True Faith or be condemned. He will not be very tolerant.
And, yes, it will take a few years before most sedevacantists accept him as a true pope.
Another possibility is that the Vatican will finally do something that even the SSPX cannot accept and I think it will be to allow the ordination of women. This is when a large number of sedevacantist groups (which will now include the SSPX) will elect a true pope who will govern the true Church from Rome and the Conciliar Church will whither away in a matter of just a few years. Soon, the secular Vatican will invite the true pope to lead them.
There is also the possibility that there is a true pope whom we don't know. I find this the least likely possibility.
Of course, there is one other possibility. The crisis will end with the coming of the Final Judgment. This is not the resolution I wish for as I am not ready for judgment.
As for other theories, they may be as equally plausible as any of these. I can, however, imagine Catholics asking these same kinds of questions during the Arian Crisis and Catholics in England asking these kinds of questions during Elizabethan England.
When a new Conciliar pope is elected, I will listen and watch. If he continues down the road to destruction, I'll continue as I am. If he makes an about face, I will look at him with renewed interest.
I hope that answers your question, at least as far as I am concerned.