From the American Journal of Archaeology, some new Ara Pacis scholarship:
"The Ara Pacis presents the most important surviving programmatic statement of the middle years of the Augustan principate. Recent scholarship has focused on the identity and significance of the altar's children, but progress has been constrained by assumptions about Augustus' dynastic ambitions. The altar reflects the political realities and ideals of the year 13 B.C.E., when adult generals were in ascendance, foreign children took center stage, and the political prospects of Gaius and Lucius Caesar were still uncertain."
There is a little more here, and it seems the full article will be posted in PDF format at some point.