Certainly. Though I would say that your "would" should be changed to "could." And then I would qualify that by saying that we're talking about Protestants who are ignorant of the truths of Catholicism. Those who willfully reject the Catholic Church, even as Protestants, cannot be saved, because, rejecting truth, they reject Him who IS Truth, at least as He would have Himself known to us.
But, again, such rejection must be willfull and conscious. The vast majority of Protestants today do not fall into that category, I'm sure. But I would make this observation: since they do not have the same grace bestowed on them as a Catholic who avails himself of the Sacraments (especially the Eucharist and Confession), I wonder how much more difficult it is for Protestants to actually be saved. I have no idea, of course. This whole thread's theme presupposes the availability of God's mercy. But, while I have the moral assurance of salvation as long as I'm in a state of sanctifying grace, I would never have such assurance as a Protestant who cannot avail himself of the Sacraments.
We all sin, no one remains sinless for long after the initial cleansing of baptism, so I would feel far less sure of where I stand as a Protestant without sacramental reconciliation with God than I would as a Catholic who can, in fact, avail himself of such reconciliation. Therefore, while I certainly concede that Protestants can be saved, I wouldn't even want to speculate about relative numbers. And, in any event, I can say that, if they are saved, they are saved in spite of, not because of, their imperfect communion with the Church Christ established.
The Orthodox dispute the primacy of Rome, and they are still part of the church....They KNOWINGLY do not adhere to Roman teachings and instructions.
Are they all lost?