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: