What about Golden Sun's elemental psynergy? This gets into the important point on the TV tropes page under Anime & Manga – East Asian media often conflates spiritual power, wizardry, martial arts, and psionics into one thing because there wasn't as much of a push back against esotericism as Europeans had with the witch hunts.
But even in the West, there's tons of examples of Pyrokinesis etc as a discipline of psionics – the important point is that the elemental magic was formed by the mind and not ritual or MSV components.
I view both power sources − Psionic and Primal − as coming from the soul. Both are strongly animistic. Both utilize the ki, spirit, and mind. But they distinguish thematically. Psionic is more human, body altering, telekinetic and dimensional, while Primal is more elemental and plant altering, wielding energies, and fabricating objects and structures.
Where "Pyrokinesis" uses the "mind" to manipulate elemental fire, this is still Primal.
This is why I think Psionics belongs as subclass archetypes across the gamut of core classes, though there should be a Psion/Mystic core class to represent Yodas & Xaviers since they're close to the Wizard concept but Wizards are crucially far too tied to their components and spellbooks and rituals to represent this power.
I agree. A Psion class plus judicious Psionic subclasses for other classes is a great approach.
I hope the Psion is a 3e-ish fullcaster, but using a 5e Warlock chassis.
I suspect the 2e-ish Psionicist might work well as a Rogue subclass, using a skill system for Psionic instead of a spell point system.
The 5e feats already have the 1e-ish powers covered.
Monks are the easiest next step to graft psionics onto.
2024 seems to make the Monk class more clearly Martial (without mentioning "ki"). But Monk subclasses can be Psionic.
And as we've seen with the Purple Dragon Knight playtest, there's multiple ways to make a Psionic Fighter in 5e lore, just as Eldritch Knight, Arcane Archer, Rune Knight, and Bladesinger can all coexist (as opposed to Valor Bard/Swords Bard and Pact of Blade Warlock Hexblade Patrion Warlock really being patches that are meant to supplant or enhance the other one). I could see Psion either appearing in a Rules Expansion book a la Artificer in Tasha's, or else in a book like Fizban's or Bigby's, with a few other character options that support Psionics and a bunch of Far Realm entities for your game.
For me, Psionic is all about ones own self being the power source. So I dont see the connection with the Farrealm, except that some of them happen to be Psionic too. As aspects of thoughtscapes, Angels, Fiends, and Aberrations are all Psionic for similar reasons.
Oh and unrelateded to Yarael's post, someone said Dark Sun has been 'cancelled' – as much as I think the setting is problematic in many ways, it's also a beloved setting and part of D&D Lore and appears by name in the 2024 DMG, so it's certainly a planned setting to explore at some point. The main D&D setting that was 'cancelled' is Nerath because there's just not a lot of reason to include it if you're putting Greyhawk in the DMG and besides, you've mined Nerath for its best original stuff already (Feywild & Shadowfell, Astral Sea, Raven Queen, core Dragonborn, Tiefling, & Goliaths). Nerath struggles to fit into modern D&D because it changed so much to support the sacred cow slaughters of 4e (their words, not mine) while also borrowing from Greyhawk and Mystara wholescale for iconic setting elements. I swear, the principal reason we don't have Dark Sun yet is because they want to get Psionics right first.
Too be honest, 5e kept the good aspects of the 4e cosmology. 5e has the salient Feywild and Shadowfell, but additionally returned the Ethereal from earlier editions, which I feel works better in the new ensemble. The shape of the 5e "circle" cosmology feels more pleasing in a jungian mandala way.
You are probably right that the delay of Dark Sun is mainly about how to do the Psion. I was surprised to see 2024 mention Dark Sun. Perhaps this indicates a more confident way forward for how to design the Psion? I prefer the 5e Psion class being in a Tashas-esque rules expansion, so it doesnt get tied too tightly to any particular setting. Several setting need the Psion class.