After explaining the promises to Israel in the New World, verse 29 had focused on Israel in the Old World. Here Jesus speaks of both the New World and Old World branches. The covenant promises will be kept to both, but the Old World house of Israel must accept the gospel. Therefore, it will be preached to them, and they will accept Jesus as their Messiah. The witness of their understanding will be that they “shall pray unto the Father in my name.”
The Jews certainly pray to Yahweh. That will be nothing new for them. They believe in Yahweh. The difference is that they will understand and accept the Atoning Messiah’s mission—hence the significance of praying “in my name.”