Historically, the USN developed rapid-fire 6" and 8" guns late in World War 2, and introduced them in service in the latter part of the 1940s.
The RN introduced a rapid-fire 6" somewhat later, with limited service on cruisers.
My knowledge of the design of naval artillery is rather limited, so I'm going to ask y'all here: Is there a practical size limit for automation of naval artillery? Could the RN have developed a 9.2" automatic, or Bofors an automatic 10"?
I acknowledge the market might not be there for such weapons by the time they're possible; it's the technical feasibility I'm interested in.