I’m basing this on a comment by my old Protestant pastor. He once confided to me in his office that he “wondered if Protestants get into heaven.” Apart from any direct spiritual sense or doubts he might have had, his argument was that he thought God was not as easy-going about the division of the Church as we are. In particular the Reformation was, in his words, “easily the most violent episode in church history.”
Now for him to make such a comment, and konwing how accurate he usually was, with a reputation for holiness and wisdom (even my Catholic psychiatrist said to me, “Whenever I heard Rev. Missenden mentioned in church circles, it was always with the greatest respect”), he’d have had sincere doubts. I had a brief vision of him after his death (one of a few), in which he appeared, and said, “We’re not in heaven. Oh, we’re not in any pain, so you don’t have to worry about that. In fact, it’s pretty good around here” (and his expression at the time was one of considerable enjoyment), He then repeated, “But we’re not in heaven.”
Exactly what I’m supposed to do with that I’m not sure.
But the fact is that Protestants persist in dividing the church, ignore Christ’s statement to Peter about being the Rock, never fully participate in the Eucharist or Christ’s body and blood ("He who does not eat my flesh and drink my blood has no part in me". That’s not just symbolic.) and often tell lies about Catholics and the Catholic church. In fact, the old pastor said, “Protestants can be arrogant at times. They tell a lot of lies about Catholics and the Catholic Church”. Lying is a sin, particularly if it is unconfessed.
He also commented about the approved Marian apparitions. “There’s been a lot of them. I think they’re a judgement on a divided church”.
So for all CS Lewis’ holiness, and that of my old pastor, my own belief is that he, and every other sincere Protestant, is camped just outside the Pearly Gates, and that they won’t get in until the churches formally unite. The same would apply for Dietrich Bonhoeffer, William Carey, Albert Schweitzer, and every other Protestant. And a lot of them were exceptionally good Christians in every other regard.
I personally think the answer is “No.” When my father in law died, I had a similar vision, in which he was told he’d have to wait. He was a good man, and a Baptist.
But as I said above, exactly what I’m supposed to do with all this, I don’t know.