But if the Star Trek brand still continues because of new shows and new characters isn't that what is most important?
But will it? Even with all the later shows that have come along with their own distinctive casts, it's still TOS that's the most popular and iconic incarnation of the franchise (though TNG comes close). Look at the diminishing returns the later series had in terms of ratings and popularity. And TOS books and comics are still the strongest sellers compared to other series, which is why IDW and TokyoPop didn't even bother to license anything other than TOS and TNG (well, IDW did put out one DS9 miniseries, but it sold poorly and they haven't done another).
So why fight it out of some misguided purism? If audiences continue to be interested in TOS, why not give them what they want and keep TOS around as a living, breathing franchise? After all, for plenty of fans, it's not the abstract universe that appeals to them, but the particular characters.
Besides...don't all good things come to an end eventually?
Not necessarily. We still tell stories about Hercules and King Arthur and Rama and the Monkey King and the like centuries or millennia after the original tales were told. Because they kept getting
retold and reinvented for new generations and new audiences. This is how human beings have
always kept stories alive: by retelling them, keeping them fresh and current. Remember, for most of our existence as a species, we didn't have writing, or at least didn't have widespread literacy. The natural, original way for human beings to tell stories was orally, and in oral storytelling, the tale changes every time it's told, as the tellers add something of their own, something tailored to their audience. That's fundamental to the way that human culture transmits its lore. The idea that a story needs to be fixed and unchanging is a comparatively recent conceit developed by literate societies that see stories as something contained on paper -- or these days, on film or video or flash memory -- rather than something alive within the human mind. But even so, stories that originated on paper have been reinvented and transformed many times, as plays or radio shows or movies or TV shows or whatever, because that deeper impulse to let stories live, breathe, and evolve is still embedded in our psychology.