What happens to the people who die in the midst of a season of discernment about becoming catholic?
Well, I am aware of baptism by desire for those called to communion with the Church but who die prior to reception of the sacrament. This typically applies to RCIA students, and their intent is seen as sufficient.
I’m not 100% sure prior to that choice being made, but for those being called but have not yet committed, I think we entrust them to God, but not sure we can say with certainty. God will evaluate. A baptized Christian would also already be in some communion already with the Church.
God takes us from where we are, knowing where we would’ve gone, knowing us better than we know ourselves. He judges by the heart as Scripture tells us-and only He knows with certainty whose names are written in the Book of Life, and whose are not.
From the Catechism of the Catholic Church, paragraph 847:
Those who, through no fault of their own, do not know the Gospel of Christ or his Church, but who nevertheless seek God with a sincere heart, and, moved by grace, try in their actions to do his will as they know it through the dictates of their conscience - those too may achieve eternal salvation. (source)