As another pointed out you are less at risk of having your mileage balanced wiped out (if AA goes bankrupt they will either be absorbed by another airline or will restructure/shrink), more a devaluation of your miles. Anything you do to move your balance of miles out of AA would likely create a larger haircut than the devaluations you would endure in the worst case by sticking with AA - they know their mileage programs are cash advancing lifelines so will keep the devaluations small for now and ramp them up later so just look to work down that balance over 2021/2022 while you can.