For my ships I just put a (1) in front of the number I actually want on the registry. Like my Akira-refit escort carrier which was originally built before the Dominion War has the registry NCC-(1)68636. And my Sci officer's Intrepid-retro USS Ray Bradbury is registered NCC-(100)451-F.
So what happens if a new Star Trek series comes out with ships in the 90k range?
LOL Good one.
Tragically, we will very likely never see another big-budget CGI-intensive sci-fi series on network television.
CBS's biggest hit is NCIS, in which the most expensive prop they use is Ducky's '63 Morgan roadster, and yet they really don't make all that much money off of first run advertising because - thanks to TiVo and other DVRs, nobody actually watches ads anymore. So I don't believe the CBS network execs would ever authorize the necessary budget to make Star Trek The Next-Next-Generation happen.