What happens to infants who die?
I think they're all saved. In other words, I don't buy the principle that says that children born into "covenant families" are secure, and children born into "non-covenant families" aren't. I don't go there.
My reason for thinking they're all saved is because of the principle in Romans 1 where Paul argues that all people know God, and they are "without excuse" because they do not honor him or glorify him as God.
His argument is that they are without excuse because they know things, as though accountability in the presence of God at the Last Judgment will be based, at least partly, on whether they had access to necessary knowledge.
And God says they've all got access to knowledge, because they can look at the things he has made and see his power and deity. But they suppress that knowledge instead of submitting to it, therefore they're all condemned.
So I ask the question: OK, is the principle being raised there that, if you don't have access to the knowledge that causes you to be held accountable, therefore you will not be accountable? And I think that's the case.
I think babies and those with profound mental disabilities don't have access to the knowledge that they will be called to account for. Therefore, somehow in some way, God, through Christ, covers these people.
So that, in a nutshell, is why I think all children who die in infancy are elect and will be, through Jesus Christ, saved in ways that I may not know how, as God honors this principle of accountability.