Unlikely that DC3s and C47s will stop flying if they are passed as airworthy. They just cannot carry passengers without an expensive upgrade.
This URL gives “Rare Dc3s in the UK” http://www.douglasdc3.com/dc3brit/dc3brit.htm
And there is certainly no word that the Battle of Britain Memorial Flight – Douglas DC-3 ZA947 (cn 10200) is to be grounded.
I think we shall see many of these graceful birds for some time yet in the skies.