Since, Blu-ray listings only go through episode #12, speculation is that if the series does run the unconfirmed 26 episodes, it would be a split between non-consecutive seasons.
Last May, the first indication that Twin Star Exorcists would run 50 episodes came from leading Chinese streaming company iQIYI.
According to their listings, the anime adaptation of Carlo Zen and Shinobu Shinotsuki’s 7 volume ongoing light novel series Saga of Tanya the Evil is slated for 26 episodes.