I might have a bad evening roll....AFAIK (@Harvey) there's never been confirmation that Star Trek had been "cancelled" by NBC at the end of the 2nd season. Roddenberry initiated the "Save Star Trek" campaign via the Trimbles in like 1967 before they even wrapped production for the second season. I think Roddenberry feared the show was doomed due to it's low ratings and decided to proactively try to save it.