I agree with you, if Manchester united eventually win Bayern probably because bayern use theirs rotational payers knowing how risk free this match is to them and it turns in favour of Manchester united, they will still hope Copenhagen draw against Galatasaray.
Qualification is no longer in the hands of Manchester United, the best they can do is to get their own job done by beating Bayern Munich and hope for a miracle in the other game. Beating Bayern isn't going to be an easy task, i know Bayern have already qualified and they might not play their first team, but any team bayern plays is going to be a strong one, United themselves are in a bad position, they are lacking in confidence, so they might fail to win even if Bayern plays a weaker team.