It is also possible TOS will be forgotten like 60s Mission Impossible. Today when you say mission impossible , the Tom Cruise series is what most people think of. I would bet most modern audiences don't even realize the 60s show even exists.
The original M:I TV series--which ended in 1973--was a dormant property until the unsuccessful 1988 revival series which was not the result of a large public demand for M:I to return. On the other hand, TOS quickly turned into a cultural phenomenon in syndication, with viewers calling for more (hence TAS, then
Phase 2 and of course, the TOS movies), which created a genuine franchise.
A cancelled TV series returning time and time again as it catapulted to the Mount Rushmore of pop-culture was unprecedented and proved TOS earned its legendary status generations ago. To this date, no other ST series has reached that height to the point where the average person recognizes its characters and tropes.
The legacy media recognized this with
TIME's list of
The 100 Most Influential People Who Never Lived (2013). While the list included some rather questionable choices, you will note that one of the cover's featured characters are...you guessed it. No other Star Trek characters from any post-TOS production up to the year of this issues publication were included, and Kirk and Spock were not representatives for all ST characters.
2013 is not ancient history, profiles of that kind are not rare, and the kind of reverence for TOS seen around the world has not diminished. Perhaps someone should ask if other ST series will ever earn a truly legendary status in the world's popular culture.