If the SSPX is reconciled with the Vatican, the canonical practicalities will have to be hammered out. I trust the Vatican will remember to dot all the i's and cross all the t's.
One of the things that will need to be handled is SSPX marriages and annulments. Now, the Vatican could tacitly accept the SSPX's theory of "emergency jurisdiction" for something like confession under the assumption that, even if confessions were invalid for lack of faculties, people will surely go to confession again once faculties have been granted, so you might as well let sleeping dogs lie. And these wouldn't even have to be general confessions reconfessing things confessed to SSPX priests before the faculties were officially granted, because if the old sins are omitted in sincere good faith (ie, the penitent assumes the previous SSPX confessions were valid, even if they weren't) then the new absolution will cover it all, so there is no huge issue here. I also wouldn't be surprised if some trads, "just to be on the safe side," made general confessions after official faculties are granted.
Marriages, however, are another question. The Vatican cannot just wink at that situation, there has to be an official decision (or there could be a mess in canonical tribunals later involving SSPXers). I'd suggest that the Vatican simply put its rubber stamp on en masse on all the SSPX "annulments." These are trads after all, critical of how common annulments are in the US and such, I think we can safely assume all their "annulments" really did determine true cases of invalidity and so officially sign off on those conclusions without requiring a new canonical trial for each case.
SSPX marriages, however, cannot just be assumed valid. Yes, there is this claim of emergency jurisdiction, but we have to be safe. All SSPX marriages in which consent persists should be radically sanated upon any reconciliation. Those which have broken up in the meantime, where consent does not persist, pose a trickier case, however. Likely, canonical courts will just treat them as invalid and give them an easy "defect of form" annulment if they want to remarry (or already have), but the SSPXers aren't necessarily going to like this (seeing how it basically seems to implicitly refute their "emergency jurisdiction" idea).
Indeed, it could get interesting, as some of the divorced parties themselves may still be SSPX traddy types, and consider their SSPX marriage as having been valid (even though it formed and then fell apart before the granting of jurisdiction and radical sanations), and might try to throw a fit if their spouse remarries based on an annulment granted merely on the grounds of a canonical assumption that SSPX marriages (until the radical sanation) were invalid by defect of form.
It could be interesting...