In the event of a reintegration with Rome, the SSPX and the FSSP will most likely NOT merge. At this point, it is obvious, even in these times, the FSSP and the SSPX clearly have a different charism. Msgr. Berg has made it clear that the role of the FSSP and its vocation is the mass and only the mass. As a reusult, since the tenure of Msgr. Berg, the FSSP has been actively involved in training Novus Ordo priests to say the Tridentine Mass. They have completely washed away their original vocation and original goal and have now become, for the most part, a training group for novus ordo priests. Their Seminary holds multiple workshops every year to train Novus Ordo priests. The SSPX, on the other hand, has never done such apostalate. Unification of the two groups is almost impossible. It's almost like saying that, if the SSPX gains a place in Rome, all the traditionalist groups will de facto fall under the SSPX unbrella, like Bon Pasteur, ICRSP, etc. They each have their unique charism and I doubt the SSPX will be much receptive to them.