The poll is useless. If he wanted to step down as CEO, he would have already made up his mind and had the next CEO lined up, using this poll as a formality. Had he not intended to step down, then it seems to me he won't abide by the results of the poll.
It does seem very likely that he had already decided to step down, and that the poll is simply yet more publicity.
The question is, who would want to take over, given that Musk is still, of course, the owner?