C.E. Evans wrote:
Actually, we don't know that at all. All we know is that Excelsior was the first. A second Exclesior-class ship could have been waiting in the wings in the final stages of construction at the time of Star Trek IV, and that ship became the new Yorktown.
So Starfleet is building multiple Excelsior
-class starships based on a technology that hasn't been proven in the field?
That's what they did the NX-class, the Galaxy-class, the Defiant-class.
Really, by the time a prototype completes her shakedown and enters actual service, mass production can begin at any time. NX-01 aside, the NX-designation for a prototype is really only necessary for a short period of time, IMO, and changing it to NCC is probably more an instance of doing it at a convenient time.