From what I recall from years past, an edition year is usually the most busiest for AoS and where they are trying to release their full slate on time before the edition change during the summer. Then it followed up by a 6 month lull in release and picks back up during the next year with the battletome train and a few releases.
AoS 2.0 had Maggotkin, DoK, Deepkin, Malign Portent, then Soul war release with NH and SCE.
AoS 3.0 had Broken realm with multitude of big character models, LRL wave 2, Soulblight gravelords, Dominion with Thunderstrike and Kruleboyz.
And AoS 4.0 had the rest of the Dawnbringer books plus special character boxes, FEC release, the last minute Darkoath box, and then of course the new Boxset with more SCE and Skaven.