Nah, the final arc is huge, far too long for even a 2 cour season, and there's still a mini arc before that to tie up a loose end from season 3. Plus, I doubt they've storyboarded any of the unreleased chapters yet. At a guess I'd expect this to be 13 eps, then a couple more years wait, then a 2-cour season and finally a tie-in movie to finish. That being said we still don't know how many chapters remain so it could go on longer than that.