These things are never predictable.

The key is to simply head for the new departure gate as quickly as one can. Even if the flight shows as closed. If, indeed, the flight is closed when one gets to the departure gate, move to Plan B.

As this was a ticket departing the EU, AA would have had a duty of care to include hotel and meals, no matter what the reason for the delay. In this case, AA would also have owed the passenger EUR 600 ($660) in cash equivalent, e.g. check.