On the surface your question seems simple, but it is maybe more complex than one quickly realizes. Please read 2 Samuel 12:1-23 about the son that was born to David out of his adulterous affair/marriage with Bathsheba. The son died of an illness as an infant. David, who we know made it to heaven said in v23 "I shall go to him, but he shall not return to me." It appears that scripture supports infants going to heaven.
Note additionally that the "144k" of Revelation are followed by:
After this I beheld, and, lo, a great multitude, which no man could number, of all nations, and kindreds, and people, and tongues, stood before the throne, and before the Lamb, clothed with white robes, and palms in their hands; Revelation 7:9.
His mercy endures forever, Amen.
I really don't know how you can drag 144k into the subject of whether babies go to heaven. I see nothing in those verses in REV. indicateing babies.
The problem with quoting the Old Testament regarding unbaptized babies going to heaven is though Christ existed before the "Word was made flesh" the sacrament of baptism had not yet been instituted so we are not dealing with unbaptized children in the OT. We are really comparing apples to oranges.
This is just my thought but I look at it this way: faith comes through hearing, so a dead child (a stillborn or a child that has died before the age of cognicent thought)would not have known of Jesus Christ and had no input on whether to deny Christ and reject baptism. So, in this case the child would not be guilty of disbelief (unbelief or whatever you want to call it) and this unbelief is what really damns the soul - this rejection of Christ.