User blog comment:Adsper/All Possible Mobs/@comment-2601:146:301:43B3:BD2C:7D64:F421:C900-20190729014016/@comment-2605:A000:A487:EC00:643F:7518:E78:3561-20190806171535

There are no certain release dates. They post stuff about this on Twitter about once every few weeks.