I never liked the idea of canceling the NX program (why cancel your heavy cruiser class during the middle of a war?)
At any rate, after the space shuttle line, I always assumed the next set would be named after the original six frigates of the USN.
Why? In fact, if we jump from pre-unification space programs to pre-unification navies, wouldn't the British Royal Navy be the one that would be regarded as more historic than the U.S. Navy, since it was the first modern navy? If the United Earth Starfleet named its NX-class ships after the U.S. space shuttle fleet because of their status as the first reusable space ships, it would make more sense to assume they'd be naming ships after the first modern navy's ships rather than just naming them after the U.S. Navy ship's just 'cos.
Makes sense. I'm using Greek gods for my NY-01 Daedalus class. Daedalus, Icarus, etc...