‘And Esau hated Jacob because of the blessing with which his father blessed him, and Esau said in his heart, “The days of mourning for my father are at hand. Then will I slay my brother Jacob.” '
As we have seen earlier, Isaac thought he was near death, and it is clear Esau thought likewise. ‘The days of mourning for my father are at hand' means exactly this. (Probably no one thought that Isaac would linger on another twenty years or more. But he did, and by the time he died all the differences had been settled).
Thus Esau decides to wait until then before carrying out his plan to kill Jacob. He does not want to distress his father. But he clearly lets his thoughts be known, for word gets back to Rebekah and she decides to send Jacob to a place of safety.