Someone can wait-list for an accessible room, but they will not bump you from it to give to someone else, especially at concierge level. Unless booking a GTY or *GT where you allow DCL to choose your stateroom, basically staterooms are first-come/first-served and once assigned not likely to be changed (yes, at lower levels there is possibility to be given an upgrade to another stateroom category if DCL decides to, but not going to happen to concierge). Unfortunately, many reservations may not actually indicate what the passenger's need is regarding H/A or whether a passenger in that party really "needs" the H/A room, so DCL would have to way to know.
You can either take the upgrade and feel comfortable with the idea that DCL assigned it to you, or you can decline because you don't want the H/A room. Unfortunately, there's no way to guarantee that a passenger who needs H/A will get the room if you decline, or if you accept no way to know that it wouldn't exclude such a passenger who tries to book next week.