Besides, it's probably hard to find a modern SFTV series that doesn't have characters making references to Star Trek as a fictional series at some point.
Past references aren't enough to stop crossovers; there's been several Trek
references on Doctor Who
, but there was still consideration of trying to do a crossover episode (before Enterprise
was cancelled), and IDW later released a TNG/DW crossover comic.
(And past crossovers aren't enough to stop references. The lead character of In Plain Sight
cameoed on Law & Order: Criminal Intent
before the show aired; but my understanding is that the writers of IPS later made reference to Law & Order
as a TV show.)