I wouldn't read to much into the assigned plane at this point. They can and do frequently swap them out day of, including within hours of departures. They also tend to avoid cancelling TATL flights if they can, since the cancelled flight in the opposite direction is going to cost them additional in terms of EU compensation. As you've noted, AA1799 has been cancelled the past couple days meaning each day they've been short an A332 in PHL, but have still managed to operate AA722 on those days. This mean they've still had a plane to fill in for the PHL-DUB segment. It looks like on Wednesday they even subbed a A333 in place of the A332; I would think it's more likely everything is zero'd out in anticipation of a potential equipment swap rather than a cancellation.