Not exactly a cancelation, but Star Trek TNG. All of the characters were far more developed than TOS's, which is why they didn't work as well in movies. Better for them to have their own episodes than to unsuccessfully have them share a movie. Any of them could have been just as good, if not better, as multi-part episodes.
I'd say that's mainly a consequence of needing to produce so many episodes per season, not an indication that there were no stories left for the characters.