God's promises to Abraham WILL be fulfilled, regardless of how faithless Israel is on occasion.
Just before the Babylonian Captivity, Israel abandoned God and He allowed them to go into captivity and 70 years later brought them back.
God is NOT done with Israel and has not abandoned them.
His faithfulness us is not based on our faithfulness to Him.
Gods promise to Abraham HAS been fulfilled. It was fullfilled in Jesus Christ, not an ethnic group. You have been misled.