Just got the same email a few hours ago!
I got the same email a few hours ago as well! I did not do anything involving USAirways or anything at all for that matter. I also wonder if it is a security breach that they haven't announced. I have no idea if this is related, but earlier today when I logged in it said January 2015 would show my YTD 2014 activity - but it was all zeroed out. Thought that was strange.
I have not called anyone at AA yet, but I was getting ready to book a couple of trips so probably should. If I hear any additional info that has not been posted by then, I will share.
Was also wondering if it was a legit email or a bogus one. However it stated my mileage balance in the email and that was accurate, for what it is worth.