On the other hand, SSPX might get a better deal from another pope - or the next after that, as the Vatican II generation is replaced by more orthodox people.
SSPX has said they need 1) acknowledgement that an indult is not necessary, since Pius V approved the Mass for perpetuity; and 2) revocation of the excommunications, which would follow pretty much anyway from 1.
It appears that some SSPX priests, in the birthplace of the SSPX, are not willing to take that chance.