Andrew there are still promises to be fulfilled even in the New Covenant. The Covenant of Grace does have some finality that is fulfilled in the various Administrations as Abraham has some finality found in Moses. The phrase, "until the consummatio saeculi," I believe proves my point. There is a final consummation of the Covenant of Grace to happen. I may be mistaken but that is how I am understanding the situation.The NC is the consummation of the CoG. It is the finality of the CoG until the consummatio saeculi.
7.4. This covenant of grace is frequently set forth in Scripture by the name of a testament, in reference to the death of Jesus Christ the Testator, and to the everlasting inheritance, with all things belonging to it, therein bequeathed.