Resistance a gateway to sedevacantism? Not directly. That is mostly dependent on what comes out of Rome, as far as the fence sitters. The former Society priests, that I know, who have embraced sedevacantism, did so over the course of many years and it was a gradual realization. Most priests who have left the Society go in the opposite direction.
Granted, many who leave the SSPX and the Resistance will find their way back to diocesan-sponsored TLM communities. But among those who remain committed to resistance - and here I am thinking more in terms of laity than of priests - is the Resistance a gateway to sedevacantist chapels?
I am thinking primarily in terms of availability, stability and convenience.
That depends on a few things. There are little tiffs within the Resistance that might make certain sedevacantist chapels appealing, I don't know if they will fizzle out or ever become a major factor--I'm thinking mostly of the Holy Week issue here.
The biggest factor would probably be the individual, does he care about the truth of the matter, or does he want to tow the party line? Has he been exposed to anti-sedevacantism and does he believe those arguments without question? What does he believe the status of sedevacantists to be, are they Catholic or not? Is he willing to change based on new evidence, in the form of Bergoglio's actions or Catholic sources?
I don't think I've been anywhere yet since the Resistance began that has reported an influx of SSPX refugees. If they aren't going to the SSPX and are waiting for that annual mass, while CMRI or other options are available, they are probably staying home.
I find this so ironic because most sedevacantists who deal with irregular mass availability have no problem with SSPX or even Resistance masses. You do not see this the other way around, old habits die hard. Though, as a sedevacantist, I would be concerned now of being denied Holy Communion at Fr.Pfieffer's masses in the future. That, and his
outstanding sermons (I definitely wouldn't want my children to hear some of the content) would keep me away.