I believe your questions have been answered.
i would recommend that you do not use the probability of winning a Move up bid in your cruise decision. (Although I am sure Celebrity would prefer that you do). If you would not not be perfectly happy with the cruise, cabin, perks, and amenities included with your purchased cruise, I would recommend that you do not book. I am fairly confident that most people do not win bids and as the cruise business increases, I would expect the probability of winning a bid to drop dramatically.
Book what level you really want and then submit a bid for a dream upgrade, expecting not to win.