When you look at the average rating over the whole season, it was the highest rated CW show for the year. So it would have to get really bad ratings wise to be cancelled.

I mentioned this in another thread, but they need to stop the season-long villains. That is getting very repetitious and tedious to do that every year, and it removes a lot of the suspense from episodes when you know the villain can't be defeated because they have to survive until the season finale.