User blog comment:KillRoy231/No no NO! Season 13 now?!/@comment-1149167-20160504033431/@comment-1031724-20160504045716

All shows need to end eventually. The Simpsons has 27 seasons, and Pokemon is only two short of 900 (not counting the banned episodes Beauty and the Beach, Legend of Dratini, and Electric Soldier Porygon).

Otherwise, they get too hard to keep track of, too hard to marathon or be watchable, pick up all seasons if you're a newcomer, etc. For this reason those following Pokemon stop after Johto. Plus, it could eventually get stale. I'm not sure who they intend the villain of Season 12 to be, whether Lucifer or Amara lasts Season 11, but still