After a slightly anti-climactic season finale for “The Vampire Diaries,” which earned the lowest finale ratings in The CW vampire drama’s history, many fans may be wondering if it’s time to bid adieu to Mystic Falls and its inhabitants.Ratings have never been an overly important issue for The CW, which is why so many fan-favorite shows have survived for so long on the work. “The Vampire Diaries” could conceivably continue on to Season 12 like its spooky counterpart “Supernatural,” so long as everyone involved wants to keep plugging away.