The Posuk says(27,41):
יִקְרְבוּ יְמֵי אֵבֶל אָבִי וְאַהַרְגָה אֶת יַעֲקֹב אָחִי:
Translated as:"Let the days of mourning for my father draw near, I will then kill my brother Jacob. "
The question is why wait until then?
Jake's good answer lists two possibilities. Some more:
The sefer Sifsei Kohen here writes that he heard someone explain (דרך הלצה) that Eisav said to himself: If I kill Ya’akov now I will have to observe a period of mourning for him, and when my father also dies I will have to observe another period of mourning. Therefore, I won’t kill Ya’akov now but rather “let the days of mourning for my father draw near” and then I will mourn for both of them together only once instead of twice.
R. Shlomo Kluger in his sefer Imrei Shefer writes that:
Eisav could have killed Ya’akov even while Yitzchok was still alive, but the reason why he delayed, saying to himself that when “the days of mourning for my father shall draw near I will kill Ya’akov, my brother” is because he knew that when he kills Ya’akov he will be very happy, and on the other hand he knew that when his father dies he will be greatly distressed. Therefore he wanted to delay Ya’akov’s death until his father dies, in order to alleviate the distress that he will experience on his father’s death by killing Ya’akov.
This is what Rivkah was saying to Ya’akov: “Behold, Eisav your brother is consoling himself with you by killing you” - he is planning to console himself at the time when he will be in need of consolation - when his father dies - by killing you.
Translation taken from here.