It is still a question, whether or not it is to be answered. Yes it would still have a question mark since it is still a question. You still try to answer it but you just realise they do not want an answer.
Sorry , I misunderstood your question. In most cases a question mark is followed. I didn't see any rhetorical questions without one. But it could be possible that there are also some without a question tag. Please wait for a grammar expert