Many today are of the opinion that deceased infants who never received baptism can be saved. Hence, they have a hope that this is possible.
The issue is complex.
One important text that presents a difficulty for such a hope is the Council of Florence, an ecumenical council.
It declares, “Concerning children, because of the danger of death, which can often happen, when there cannot be for them another remedy except through the sacrament of baptism, by which they are saved from the dominion of the devil and adopted as sons of God, [the Church] admonishes parents…” not to delay until the 40th day.
(And how many people delay for several months these days.)
Note that the text delares: cum ipsis non possit alio remedio subeniri, nisi per sacramentum baptismi. There cannot be for them another remedy than baptism.
Can this text be squared with the hope for their salvation in Christ?
I do think this is a very sobering text.
We also have the declaration of the Church that “The souls of those who depart in actual mortal sin or in original sin only, descend immediately into hell but to undergo punishments of different kinds” (Florence, Old Denzinger # 693). This “different kinds of punishment” is understood to mean that such infants, not having personally sinned, are punished with the absence of vision. They are, many propose in a kind of Limbo. They enjoy natural rest, but have no awareness of their supernatural loss.
The category “Only original sin” means infants: Those who never acted freely but died without baptism. Now, this category is empty if every infant who died without baptism is saved. But it is rather unfitting for a Church teaching to be simply empty.
Hence, it is theologically safer to say that no such infants are in heaven. Perhaps there is warrant in some cases to hope and pray for their salvation. For instance, a devout Catholic couple who has lost a child. They intended to Baptize the child. Perhaps Almighty God in his mercy will save this child.
This much is certain. That there is no promise made to these infants. Thus, the weakest statement we can make is: Church has no knowledge that they can be saved. A stronger reading of Florence is that the Church has declared that she knows that there is no remedy.
How far we are today, with our presumptions, from such sobriety. Delay not their baptism. Thank God for his mercy, do not presume on it.