Seed is common biblical terminology for offspring, children, decendants. Seed is the instrument for begetting "after its kind." The Greek word for seed is "sperma".
The text you refer to (echoing 10:16) states clearly the necessity of regeneration (heart-circumcision) for anyone to really love Jehovah, to be in a saving relationship with him. The promise is one of restoration for those who have been carried away captive, punished for unbelief. It also echoes Gen. 17:7, "I will be...a God to thy seed."
The passage is not only a prophecy although, that element is there--but remember, from the standpoint of Moses' declaration, there is no necessity for apostasy; the curses promised from Mt. Ebal follow the blessings promised from Mt. Gerazim. God declares that even after the worst judgments he sends, the covenant may yet be renewed.
Listen to the apostle John: "Greater joy have I none than this: to hear of my chidren walking in the truth" (3 Jn. 4). If a spiritual father (cf. 1 Cor 4:14-15; 2 Cor. 6:13) feels so about his children, how much more does the biological father of a child rejoice in his child's growth in grace and favor with God, as well as in stature and favor with men? Is this not (after one's own salvation) the blessing of blessings? "NO GREATER JOY!" See also Is. 59:21 for expansion on the theme, and which brings us into connection with the New Covenant blessings, as Rev. Goundry points out.
[Edited on 1-3-2006 by Contra_Mundum]