This is referred to as "Replacement Theology". It is false.

There is plenty of Old Testament prophecy still coming since it talked about both suffering and conquering messiahs. Jesus suffered at his First Coming and will conquer at His Second Coming.

As Paul explained to Christians in Romans 11, The Jews have experienced a "temporary and partial hardening of their hearts" which will continue until "the fullness of the gentiles has come in." Then God will resume with the 70th week described in Daniel 9 which will be focused on the Jews as "His holy people". And thereby "all Israel will be saved".

For if you were cut from a wild olive tree, and contrary to nature were grafted into one that is cultivated, how much more readily will these, the natural branches, be grafted into their own olive tree! I do not want you to be ignorant of this mystery, brothers, so that you will not be conceited: A hardening in part has come to Israel, until the full number of the Gentiles has come in. And so all Israel will be saved, as it is written: “The Deliverer will come from Zion, He will remove godlessness from Jacob.…

Take a look at Ezekiel 48, for example: It describes the allocation of land when Israel is reconstituted under Jesus their Messiah. This was written a couple hundred years after all of Israel (except Judah, Benjamin, and Levi) had been conquered by the Assyrians and dispersed across the world. These are the Lost Tribes of Israel and they have not yet been found nor do they currently even know who they are, so they have not yet been returned to Israel (only the Jews, so far). Thus, a very important prophecy has yet to be fulfilled.

Note that this allocation is different than the one Joshua implemented when they first received the Holy Land. It is still coming. Note the square in the middle of the map. This is where Jesus Himself will rule... in the near future.

Ezekiel 37:15 The word of the LORD came again to me saying, "And you, son of man, take for yourself one stick and write on it, 'For Judah and for the sons of Israel, his companions; then take another stick and write on it, 'For Joseph, the stick of Ephraim and all the house of Israel, his companions.' "Then join them for yourself one to another into one stick, that they may become one in your hand.…

Israel and Judah have not been "one stick" together since they broke into two kingdoms when Solomon died back around 900 BC. The reuniting of all 12 tribes of Israel into "one stick" in the Lord's hand has yet to happen.

Stay tuned!