Answer

God is not done with Israel and the Church is not the new Israel.

God has simply set Israel aside for a period of time as the channel of salvation to the world, and now the Church is temporarily the channel of the gospel message during this age of the Gentiles.  However, in the future, after the Rapture of the Church, God will again use Israel as the sole channel of salvation to the Gentiles.  This will take place during the Tribulation Period and continue during Christ's Millennial Kingdom, as He turns back to Israel (as a result of their salvation and acceptance of Jesus as the their Messiah) and fulfill the promises He made to her in the Old Testament, and use Israel as the "channel of salvation" to the world.