An offer of entering in remains. Entering what? The promised land? No, entering into the spiritual rest of God.
So the promise of a physical land represents, more importantly, a promise of spiritual rest: to know the Lord, to have your salvation settled, to have peace with God now and for all eternity. That promise says the writer of Hebrews was open in David’s time: Today, you must enter in; today, you must seek and find salvation, the kingdom of God, the rest of God, and it is still open in our day.
The letter to the Hebrews tells us that David wrote Psalm 95. If you were to turn to Psalm 95, you wouldn't find an ascription to David over the top of the Psalm, but it was. It was ascribed here to David and the writer of Hebrews points out that David is using the same promise.