Concerning Covenants

On occasion I have had conversations with folks about Replacement Theology - a belief that the New Covenant replaced the Old Covenant. In those times I have often referred friends to my friend, and one time pastor/mentor, Michael Sullivant. I refer you to his blog where he comments on a passage in the eleventh chapter of the book of Romans:

In God's economy of his historical callings and dealings with humanity...there is essentially one dominant and everlasting covenant (the rich, ancient and well-planted "olive tree") that he has made with us...though there are nuances and admittedly surprising and progressive features to its outworking over the centuries. This belief is grounded in the way that Jesus and his apostles authoritatively rehearsed, interpreted and utilized Old Testament scripture. The covenant that God cut with Abraham...a non-Jew and the father of true faith...is central to this paradigm. Certainly the Law that God gave through Moses can be viewed as another "covenant", but our understanding of its purposes must be nested into the larger "Abrahamic" meta-narrative of redemption. (Galatians 3 and 4 deal with this head on...as does Romans 4.) This also holds true for our understanding of "covenants" that God made with Adam (in the original creation mandate), Noah (in the aftermath of the flood and reaffirmation of the creation mandate) and David (in God's promise to have one of his "sons" sit on his throne forever).

Michael's teaching in this area has really helped me understand the big picture and big story of how God has covenanted with humanity. What do you think of this idea?