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followed -- or will be released alongside -- a new "8.5 edition" with the main rulebook being updated, as it is 2 years out of date now.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 focuses on how the Great Rift has made things harder for the Aeldari -- the Asuryani, the Drukhari, the Harlequins, and the Ynnari. Among other events, we have Drazhar deciding that a Phoenix Lord's head would look good in his trophy room and settling on Jain Zar to be the lucky donor, but the main focus is on the Ynnari, as Slaanesh moves to thwart their attempts to awaken the God of the Dead. Yvraine learns that the final Cronesword is in Slaanesh's clutches and just barely survives a confrontation with the Keeper of Secrets Shalaxi Helbane - only to learn that the daemon was holding back just to fuck with her.
This is a boxed set that is providing 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. Also included with the set are some new Hellions and Scourges, as well as three transports: A Falcon, a Vyper and a Venom. Alongside the campaign missions, this will also include new "Successor Chapter"-like rules that let you piecemeal together new properties for custom Craftworlds, Kabals, and Covens.
Faith & Fury
Faith and Fury is poising itself to be another Mehrens vs Khayoss Mehrens fight over a planet called Talledus. From what we know so far, there's going to be a bundle of updates for the Black Templars (who were not included in the Imperial Fists Supplement of the 8.5 Marines Codex) and the Traitor Legions (besides the Black Legion, who got their new toys in Vigilus Ablaze) that don't have their own independent Codexes, along with a couple extra Stratagems for vanilla Marines in general.
Blood and Talons
Blood Angels vs. Tyranids, Round 2. The Tyranids still haven't been purged from Baal, and there's some very serious concerns among the Chapter leadership about how the Blood Angels will survive against such an intractable plague. In fact, there have been suspicions that there's something inside of Baal that's responsible for attracting the Nids not unlike the Pharos.
Rules-wise, we are aware that this will grant the Blood Angels the tools that the 8.5 Marine codex has, making them even more of a chapter of walking blenders, with the Flesh Tearers gaining a few tools as well. The Tyranids, on the other hand, get to ride the "Custom Hive Fleet Rules" train that proved wildly popular elsewhere alongside a bundle of other rules to keep up with everyone else.