hmm, i wonder if the "know the Lord" motif is meant to be emphasized to that degree. Hebrews seems to not make that emphasis, so should we? The major point of the New Covenant is the forgiveness of sins performed by the one-time mediatorial work of Christ. You're right, the RCT argument hinges on the current for the church to teach one another to know the Lord, and because this isn't seen yet, they send the NC into the future, into heaven. The problem is that covenants are supposed to be earth and time-bound. That's why they exist - for God to condescend to us, make promises and fulfill them in time so that our faith can be strengthened. For the NC to await heaven for its completion defeats this purpose of covenants. Second, if the NC needs to await some future reality, then what are we to say about Hebrews stress that Jesus' sacrifice is a completed work?
Dennis, this may not be considering of all the previous discussion, but maybe this will help in understanding.
The old and new covenants, though administered differently, are of the same redemptive substance- by grace through faith (in Christ's righteousness alone). Always have been.
Christ was implicit in the Old Testament. He is explicit in the New Testament.
Redemption is a process. It involves a series of events- election, inner calling, regeneration, saving faith, adoption, sanctification... which ends in glorification. The elect are in various stages of this process at a given point in time.
Some are regenerated and are in the process of sanctification, yet that is not complete until they receive a glorified body at the second resurrection.
Christ does not fully put death away until after His return, and the final judgment.
There yet remains for all, the second resurrection, the resurrection of the body (to receive a glorified body) at the great judgment.
This a process, and requires holding to by faith. Though received, it is not all here yet.
There is a lot yet to come- and much of the life in the church, Christ's Body, is about focusing on this mystery, being grateful for it, and strengthening our faith toward the covenant promises.
That goes for believers- and their children, presumably being raised up in the nurture and admonition of the Lord, and amidst His worship and ordinances (in the covenant community).