Psychic Awakening
The Psychic Awakening is the name of an event in the Warhammer 40k timeline, taking place during the Age of the Dark Imperium. The Galaxy, split asunder by the Great Rift, sees basically every faction in the galaxy affected in some way, either by a sudden influx of newer, powerful psykers, or by political and cultural changes as the events of the Age of the Dark Imperium causes shakeups in the status quo.
Yes, that's right, GW seems to be Advancing the Storyline, with Psychic Awakening following a similar narrative event that occurred earlier in 2019, the War of Beasts (aka Vigilus Defiant / Vigilus Ablaze).
There are rumors that Psychic Awakening will be followed -- or will be released alongside -- a new "8.5 edition" with the main rulebook being updated, as it is 2 years out of date now. In addition, there are rumors of "Codex 2.0" releases, with this being propped up perhaps in part by the Space Marines codex refresh that launched right around the time that Psychic Awakening was announced as well as the Chaos Space Marines codex released around the same time as Vigilus Ablaze.
Regardless of "8.5," GW has confirmed that there will be new rules for each existing faction, with "Each psychic Awakening expansion [focusing] on a different war zone," with each book having fluff and rules updates "for at least 2 factions." This suggests at least one of the books has only two factions, and with GW considering, say, Dark Angels and Blood Angels to be two different Factions, we could see upwards of 11 books out of this.
The first announced war zone, Phoenix Rising, covers 3 or 4 of the Eldar factions undergoing a civil war -- Craftworld, Dark Eldar, Ynnari, and maybe Harlequins, with GW drip feeding data about one of the factions each week. With 21 factions, this equates to just over 5 months of weekly infodumps.
This style of narrative updates and a somewhat stable core set of rules with updating codexes would put 40k roughly similar to the model that GW is using for AoS, for good and bad. (Mostly good.)
Phoenix Rising
The Aeldari are a psychically sensitive race, and the fragile balance between these disparate cultures has been disturbed by the Psychic Awakening. These factions have become embroiled in a full-scale internecine war for the future of their people.
Phoenix Rising is the first listed event listed as part of the Psychic Awakening and appears to be a four way civil war for the Aeldari -- the Asuryani, the Drukhari, the Harlequins, and the Ynnari. On the outset, at least, it's a pretty simple premise of Drazhar deciding that a Phoenix Lord's head would look good in his trophy room and Jain Zar is providing a very strong opposition to dying.
This is a boxed set that is providinging new Plastic Howling Banshees, including a maskless Exarch -- a Ynnari Howling Banshee Exarch, "for they walk a very different path to their Craftworld cousins", as well as a new plastic Jain Zar. We will also get new Drukhari models and rules in the form of the Incubi along with Drazhar, though they don't seem to have any new wargear or rules for the Klaivex (that we know of). Also included with the set are some new Hellions and Scourges, as well as three transports/