The suffering Messiah has already come, but we await the conquering Messiah who will be of the line of David and will rule from the throne of David, which was in Jerusalem.
God made a New Covenant but God has not revoked the covenants He made with Abraham and David.
What is the New Covenant?
Jeremiah 31:31-34
31 "Behold, days are coming," declares the LORD, "when I will make a new covenant with the house of Israel and with the house of Judah, 32 not like the covenant which I made with their fathers in the day I took them by the hand to bring them out of the land of Egypt, My covenant which they broke, although I was a husband to them, "declares the LORD. 33 "But this is the covenant which I will make with the house of Israel after those days," declares the LORD, "I will put My law within them, and on their heart I will write it; and I will be their God, and they shall be My people. 34 "And they shall not teach again, each man his neighbor and each man his brother, saying, 'Know the LORD,' for they shall all know Me, from the least of them to the greatest of them," declares the LORD, "for I will forgive their iniquity, and their sin I will remember no more." NAS
Gentiles are saved by the terms of the New Covenant God made with the houses of Israel and Judah. God is not a covenant breaker as you portray Him to be.