The implications of Genesis 15:8 are, of course, simply enormous. But how enormous? Was Abraham one of a kind? If there were others (Job, Noah, Deborah, Rahab, David, Esther, Ruth, and the other OT heroes), were his "kind" pre-Calvary figures only? And if not, then is God saving people now who don't know the name of Jesus or, if they know a name, don't take it as representing the Son of God, the Messiah, the Lord? We cannot rule out that God, in his sovereignty, can certainly do so. If the covenant God works this way, then does that mean that we can look among Jews, Muslims, Hindus, even pagans as Abraham was when God called him, and find brothers and sisters in Christ?
This is the sort of thinking that happens when you get into a deep discussion with Morgan and Walter.