Siscoe's and Salza's work has some merits, and moreover was endorsed by several Society Bishops and Priests prior to its publication.
Now, let's look at the question more carefully, especially considering a certain famous text of Fr. Ballerini, of St. Robert's school,
Step 1: The Cardinals (or at least a handful, say 10% of them) rebuke the Pontiff. The Pope rejects this first admonition of the Church
Step 2[a]: The Bishops (or at least a handful, say 10% of them) rebuke the Pontiff. The Pope [Alternative 1] does not reject this second admonition.
In such a case, the day is saved, the Pontiff retracts, the heresy is corrected - something like a solemn anathema of it should be instituted, or some kind of dogmatic profession of Faith, or Creedal requirement etc, in future, for the Pope - and the Church goes on.
But otherwise, suppose,
Step 2[ b ]: The Bishops (or at least a handful, say 10% of them) rebuke the Pontiff. The Pope [Alternative 2] rejects this second admonition also, and no longer universally accepted, at this point of time, openly and publicly declares and manifests himself as a formal heretic.
Then, as mentioned here, the Pope would fall from the Pontificate. And the vacancy of the Apostolic Throne of St. Peter can be declared.
"
“For the person who, admonished once or twice, does not repent, but continues pertinacious in an opinion contrary to a manifest or public dogma - not being able, on account of this public pertinacity to be excused, by any means, of heresy properly so called, which requires pertinacity - this person declares himself openly a heretic. He reveals that by his own will he has turned away from the Catholic Faith and the Church, in such form that now no declaration or sentence of any one whatsoever is necessary to cut him from the body of the Church. (…) Therefore the Pontiff who after such a solemn and public warning by the Cardinals, by the Roman Clergy or even by the Synod, maintained himself hardened in heresy and openly turned himself away from the Church, would have to be avoided, according to the precept of Saint Paul. So that he might not cause damage to the rest, he would have to have his heresy and contumacy publicly proclaimed, so that all might be able to be equally on guard in relation to him. Thus, the sentence which he had pronounced against himself would be made known to all the Church, making clear that by his own will be had turned away and separated himself from the body of the Church, and that in a certain way he had abdicated the Pontificate, which no one holds or can hold if he does not belong to the Church”. (Italics added) (7)"http://www.catholicapologetics.info/modernproblems/currenterrors/heretical.htm Note the bolded. So it is after one or two warnings, from the Cardinals, or the Roman Clergy, or from a Synod of Bishops, now no longer UA, that the Pope falls from the Chair.
Such, at least, is the canonical process for this case. My view is, if it goes forward, itself unlikely, Alt 1 is more likely than Alt 2.
But let's pray, wait, work and see. We know Our Lord Jesus and Our Mother Mary are in control despite everything. They will take care.