Preempting this before someone else says otherwise: no, Butterfree and pink Butterfree never died. Their supposed death in the Japanese broadcast after mating is from an erroneous translation, and both are alive and well later in the series.
in the end there will be a super great battle involving all the pokemon in the world, and then butterfree and his girlfriend will make a cameo appereance leading a massive army of bug pokemon...
