The promise was to Abraham's seed, who is Christ. God never promised to give ownership of the land to anyone but Christ. All others are guests and resident aliens and are given the right to live there in association with him
In the same day the LORD made a covenant with Abram, saying, Unto thy seed have I given this land, from the river of Egypt unto the great river, the river Euphrates: Genesis 15:18
Now to Abraham and his seed were the promises made. He saith not, And to seeds, as of many; but as of one, And to thy seed, which is Christ. Galatians 3:16
The Father loveth the Son, and hath given all things into his hand. John 3:35
The land shall not be sold for ever: for the land is mine; for ye are strangers and sojourners with me. Leviticus 25:23