Does he really? You know that for a fact? If so, then he has an obligation to come out with what he knows ... to thwart the impending consecration. Will he give Bishop Dolan a call and tell him what he knows ... just as he was warned about Urrutigoity?
I still trust Bp. Williamson, and apparently you don't (my guess would be that your trust in him was lost after the Urrutigoity mistake).
From reading Bp. Sanborn's own words online, it's clear he would always bring in another priest/bishop to help in the Great War of sedevacantism. For his part, Bp. Sanborn is VERY partisan.
You gotta admit, Bp. Williamson is correct if only accidentally. If he had stayed in the Resistance, would Fr. Ribeiro be preparing for his imminent consecration? No. But since his conscience oh-so-conveniently HAPPENED to lead him to sedevacantism, now he's going to be a young bishop. He's going to be the Big Man. The Boss. Lots of power, and the money/attention/luxuries that go with that. Hmm...
Heaven help any man who becomes a bishop when it wasn't God's idea. Especially if he doesn't have the virtues to handle the position.
I think Bp. Williamson is correct, that when a person "converts" to something and then instantly finds fame/fortune/promotion as a result, it can be highly dangerous.
The motivation for the initial conversion itself becomes suspect.