Yes. 50 minutes is fine for a domestic -> international connection at DFW, so long as your AA flight arrives on-time, or close to on-time. If you arriving into the D terminal (where BA departs from), you really only need about 30 minutes. You won't know until the day before which terminal you are arriving into. Even if you arrive into A, B or C, the transfer to D takes no more than 20 minutes.

Where are you flying from? If somewhere close by (like a 40-45 minute flight), my experience is these flights are often a few minutes early.

Also, I should note that AA and BA at DFW are very good about coordinating with each other where a passenger is coming in on a delayed AA flight. I once arrived at DFW literally as the BA flight was closing, and they sent a golf cart for me to take me from the AA flight to the BA flight. Even my bags made it.