In Overspeed, with Autopilot active, is Stall possible?
Realistically, it doesn't matter whether or not the autopilot is engaged. For any flight condition that is a valid overspeed at an authorized altitude, for 1 g flight, you will be above the 1 g stall speed. The worst cases are near the aircraft's ceiling. (Think of the U-2 flight envelope at altitude)
When you start talking about accelerated flight (more than 1 g) then an aircraft can be stalled up to the point where you break the airframe first, but an Airbus FBW system will g protect the airframe in Normal and Alternate law, (but not in Direct or Mechanical law.) For an autopilot to be engaged, you must be in Normal or Alternate law, so you won't be breaking an Airbus FBW airframe with over g while on autopilot barring an encounter with something like a massive thunderstorm or mountain wave rotor.
Assuming that the autopilot is receiving valid inputs. the answer to the question is no, as long as the autopilot is engaged, being in overspeed condition precludes stall in 1 g flight.
Caveat! I've never flown the Airbus, and am at heart a steam gauge pilot, but I've stalled aircraft from near ground level up to over 50,000 ft.
It will not hurt my feelings if you find a flaw with my logic.