I thought I would share some relevant words from 'The Life and Revelations of Anne Catherine Emmerich':
“I was present when God passed sentence on notorious sinners. Great is His justice, but still more inconceivable is His mercy. He damns only those who are determined not to be converted; they who have a spark of good will are saved... I have seen in Purgatory Protestants who were pious in their ignorance; they are very desolate, for no prayers are offered for them... I saw that by our prayer and suffering, many a soul who labours not during life, can be converted and saved at the hour of death.”
It is important for us to remember the Church's doctrine: they are saved who die in a state of grace. Who knows how many accept God in their final moments e.g. through an act of perfect contrition.
Revelation 21:27
but nothing unclean will enter it, nor any[one] who does abominable things or tells lies. Only those will enter whose names are written in the Lamb’s book of life.
Matthew 5:26
Amen, I say to you, you will not be released until you have paid the last penny.