Board Thread:Spoilers!/@comment-25926288-20170110155747/@comment-2153169-20170226011832

Castro: The basic story line of Once will be completed this season. Whether there is a continuation with some of the cast is still under consideration, and the musical will be in the third to the last episode this season.

source: https://themusicinthedark.com/2017/02/25/eduardo-castro-talks-designing-the-costumes-of-once-upon-a-time/