I recently subscribed to Bishop Williamson's "Eleison Comments" and was quite surprised by his most recent commentary (emphasis mine):
Catholics, do not be narrow. Our Lord said That sheep outside his fold have him as head.
(Note that the above seems like something Pope Francis would say!!)
But, let's consider this in light of Cantate Domino
from the Council of Florence:
"The Most Holy Roman Church firmly believes, professes and preaches that none of those existing outside the Catholic Church, not only pagans, but also Jews, and heretics, and schismatics, can ever be partakers of eternal life, but that they are to go into the eternal fire "which was prepared for the devil, and his angels," (Mt. 25:41) unless before death they are joined with Her; and that so important is the unity of this Ecclesiastical Body, that only those remaining within this unity can profit from the sacraments of the Church unto salvation, and that they alone can receive an eternal recompense for their fasts, almsdeeds, and other works of Christian piety and duties of a Christian soldier. No one, let his almsgiving be as great as it may, no one, even if he pour out his blood for the Name of Christ, can be saved unless they abide within the bosom and unity of the Catholic Church."
Note that the Council talks about an "ecclesiastical unity" and not a "spiritual unity", a "unity of charity," a "unity of Sacraments" or an "unity of faith," etc., but rather an ecclesiastical unity, which implies, clearly, a unity of Church governance, hence, law. Clearly, anyone outside of this unity cannot and will not be saved.
P.S. Bishop Williamson's article can be accessed in its entirety here:http://stmarcelinitiative.com/eleison-comments/?lang=en