I understood the cycle to be 3 Legendaries, 2 breeding events, 3 legendaries, 2 breeding events, 3 mythics, 2 breeding events… bump a tier and repeat, etc, etc, etc.
This is the 3rd breeding event since their release (counting the release event), they should be released this week.
10/16/2019___Breeding________8 weeks since release - 2nd wave should come out
9/16/2019____Breeding________4 weeks since release
9/9/2019_____Team Gauntlet - Fall Season beings
8/21/2019____Breeding________First 3 Legendary Abyssals released