For what it’s worth, my understanding based on the comments on this question, and multiple conversations I had with airline representatives (including gate agents and customer service call center folks) is that the airline has NO obligation to return your luggage in this situation.
In my case, my worst fears became a reality. They kept us in limbo for hours, then cancelled the flight after it was too late to practically drive, and most of the convenient flights to nearby airports had already gone out. To really rub salt in the wound, they sent our carry-on bags to baggage claim instead of bringing them back up to the gate, and it took them about another 1.5 hours to show up in baggage claim.
Needless to say, there was a group of very unhappy people picking up their carry-ons, trying to book new flights, and going back through TSA security.
None whatsoever if you are in the USA on an American carrier.
Credit:stackoverflow.com‘