User blog comment:HalointheSkye/Volume 3 Hiatus - Week 1 - Announcements!/@comment-25209034-20160223103730/@comment-4010415-20160223104143

I'm pretty sure they're not gonna give us an estimated premiere time for Volume 4 for a while. They've only recently started working on making Volume 4, and they can't predict any snags they might hit in production.

Think about it this way: Since we're going to be seeing new places in Volume 4 (Mistral, Haven Academy, hopefully Atlas), they have to actually build and texture those places. They also have to build, texture, and make rigs for any new characters (Mr. Schnee, maybe Pyrrha's mom) or Grimm that will appear. They have to get all of that stuff done before they begin making the episodes. Also, Miles and Kerry have to sort out the script.