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followed -- or will be released alongside -- a new "8.5 edition" with the main rulebook being updated, as it is 2 years out of date now.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. Each book effectively gives rules update to each of the factions featured in it, for example Tyranids being given the "build your own hive fleet" rules that the Space Marine successor chapters had. Codex 2.0 compiling these updates is likely.
Regardless of "8.5" or "Codex 2.0," 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. GW has further clarified at Open Day 2019 that the general plan is to add one "reborn, reimagined, (or) brand-new" character for each book (or faction), which they have generally stuck to so far.
The first announced war zone, Phoenix Rising, covers the Eldar undergoing a minor civil war -- the Ynnari having broken the balance between the Craftworld and the Dark Eldar, resulting in all three sides kicking each others' asses.
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.)
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
The Sisters of Battle and Astra Militarum – bolstered by a massive strike force of Adeptus Astartes led by the Black Templars – stand firm in their creed to defend Humanity, at any cost...
As part of GW's reminder that Sisters of Battle exist, Faith and Fury sees Kor Phaeron of the Word Bearers, alongside members of 5 other Chaos Space Marine legions, attacking the Talledus system, a region of great importance to the Ecclesiarchy on account of its ties to Sebastian Thor. Defending Talledus is the Sisters of Battle, the Black Templars, the Salamanders, the White Scars, and the Imperial Guard, although this is not the Imperial Guard's book.
Content includes updates for the Black Templars (who were not included in the Imperial Fists Supplement of the 8.5 Marines Codex), "Chapter Litanies" and updates to Space Marine "Heroes" (such as Chaplains or Librarians) allowing them to take new relics and warlord traits with the use of a specific Stratagem, as well as updated rules for the Word Bearers, Night Lords, Alpha Legion, Iron Warriors, Emperor's Children, and World Eaters. New model releases include a new Chaos Space Marine Sorcerer.
Fluff updates include the Word Bearers trying to corrupt Imperial Cults only to see the Great Rift's energies causing weird shit like Flocks of Golden Eagles or Pillars of Golden Flame to appear, which restore faith in the Emperor when they're seen -- basically, Chaos no longer has a monopoly on warp fuckery, pious Imperials can do it too, now. This culminates during the battle of Talledus when "golden faced spirits" are summoned out of the Sisters of Battles tombs, creating a shield that instantly burns any demon that touches it to ash while also repairing the walls of the immaterium (de-Chaosifying the area, like a Blank) and generally screwing Kor Phaeron over, leaving him looking stupid and calling for reinforcements.
This is further expanded upon in a collector's edition exclusive chapter that covers the Alpha legion turning an entire planet of normal humans instantly into Psykers, except their faith causes them to summon the aforementioned "good warp stuff" like flocks of golden eagles and the like, as well as the Emperor Angelic, a psychic manifestation of the Emperor that promptly fucks the Alpha Legion up. The psykers on the planet are also turned into Emperor-empowered super-psykers called the "Humble Saints" which can nuke the Alpha Legion's psykers and daemons with a wave of their fingers. But because it's still Grimdark, the Iron Hands demand these new psychic superhumans be purged and call in the Sisters of Silence and Inquisition to do so when the Sisters of Battle refuse to let them.
tl;dr: The Word Bearers discover that Imperial Faith is now summoning their own warp entities -- Golden Eagles, Pillars of Golden Flame, Golden Faced Saints, and a psychic manifestation of the Emperor himself. The Alpha Legion has a way to turn normal humans into Psykers en mass, except Chaos no longer has a monopoly on psykers. This is all held behind a CE paywall meaning that only a fraction of the playerbase will read it (unless it's put up on the website later).
Blood of Baal
In these dark and desperate times, far from the guiding light of the Astronomican, only heroes such as Commander Dante, Mephiston and Gabriel Seth of the Flesh Tearers were able to hold the defenders of Baal together.
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. Model wise, a new Primaris Mephiston accompanies this release.
Ritual of the Damned
Thousand Sons, Dark Angels, and Grey Knights. Seems like it'll take place around Prospero. Will this see the Grey Knights actually fixed? Unlikely, but faith in the Emperor is it's own reward.
The Greater Good
Orks, based on a reference to a Super-Ork. Maybe Space Wolves too, since sagas are their thing. (Space Wolves vs Orks was leaked previously, this is seemingly a confirmation.)