I don't know how much you all have thought about the changes that will happen to the Trad landscape after a neo-SSPX deal is consummated.
For example: not all neo-SSPX chapels are created equal. You have everything from your conversation pieces (St. Isidore's) full sized Gothic churches enough to impress even Indult crowds, all the way down to "missions" held in hotel rooms, and everything in between.
Moreover, each of these chapels is in different situation regarding competition with "Rome approved" Latin Masses, such as FSSP, Indult, and Institute of Christ the King.
Let's just say that a conservative Novus Ordo prelate (bishop, cardinal, Pope) -- or even a neo-SSPX official -- could more easily justify the continued existence of some neo-SSPX locations better than others. Some missions would be utterly useless, given the new standards.
If the neo-SSPX is approved by Rome, and the Indult is approved by Rome, then why would the local bishop permit a Latin Mass every Sunday in the cathedral in Austin, TX, while at the same time the neo-SSPX sends a priest 2 Sundays a month to a hotel room to offer Mass in the same city? Wouldn't that be a slap in the face to the local bishop? As if his Indult Latin Mass wasn't good enough?
And this argument would apply almost as well to ANY neo-SSPX chapel with an Indult/FSSP option in the same city -- say, within 45 minutes.
Or perhaps the hotel missions (with an Indult closeby) will be shut down first, while the dedicated chapels competing with Indult locations will be shut down later. You know, to keep things gradual and so people won't get TOO upset.
There are actually a lot of variables: chapel wealth, chapel income, how established the chapel is, what competition is there from Rome-approved Latin Masses, the size of the congregation, the distance to the NEXT closest neo-SSPX chapel or Indult location, and so forth.
To me, it is as obvious as the nose on my face that the neo-SSPX/Roman authorities would have an excellent argument for shutting a lot of neo-SSPX chapels down at some point in the near future once an agreement is made.
P.S. I would also predict that SOME (how many? God knows) Indult locations will be shut down in the first few years, once the anchor man (SSPX) in the tug-of-war dies. The SSPX used to be the uncompromising, front-line elite troops in the war against Modernism. With their surrender, ALL TRADS will feel that tug on the rope much more strongly.
Bishop Williamson used to compare the SSPX to an ugly, 400 pound "anchor man" in a tug of war. He just grabs the very end of the rope, wraps it around his hand a few times, and plants himself there. Both sides pull and tug, but that anchor man prevents (any?) progress by the other side, since they have to pull 400 pounds just to get STARTED opposing the other side's collective pulling force.
Now they've shot the anchor man dead. What will happen to the struggle with Modernism and the other errors coming from Rome? It won't be good.