As much as I respect nearly all manufacturers and the A300 design, it seems to me very unlikely that a significant number of A300/310s will be operational in 2050.
Airbus aircraft are - in my opinion - not built like tanks and structural robustness is not a ace of Airbus but other important factors. Many early A300s are no longer operated and currently Turkey seems to be a heaven for such early aircraft but these aircraft will surely be replaced by younger aircraft soon.
There is also the factor that aircraft manufacturers are not really keen to take care of existing aircraft fleets but keen so sell replacement aircraft.
Kindest regards, IB M87