Did God abandon Israel forever after they rejected the Messiah?
No. God set Israel aside and blinded them, but He did not take them out of His program. The Abrahamic covenant remains valid and will be fulfilled. He will come back and finish it. Israel's rejection of the Messiah did not cancel God's promises to Abraham, Isaac, and Jacob.
Les explains that when Israel rejected and crucified their Messiah, God did not turn His back on them forever. Instead, He set them aside and blinded them, but He has not taken them out of His program. The Abrahamic covenant, first given in Genesis 12, is still valid and true; God has not changed His mind. Christ's first coming was to fulfill those promises to Abraham, Isaac, and Jacob, and even though Israel rejected it, God will still come back and finish the Abrahamic covenant. Absolutely He will.
Now the LORD had said unto Abram, Get thee out of thy country, and from thy kindred, and from thy father’s house, unto a land that I will shew thee:
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