While Kingdom Hearts 4, it will likely take some time before fans learn more. No release date was given, and knowing how long Kingdom Hearts 3 was in development (though KH4 should not take as long), it is likely to be a few years away at the very least.
As Sora grows up in the Kingdom Hearts 4 trailer, she describes it as an afterlife of sorts for their kind. What all this means will indubitably be revealed throughout the story, while Donald and Goofy appear to be attempting to arrive to Sora (perhaps approaching Hades in the Kingdom Hearts 4 trailer). The trio will no doubt be reunited, and when they are, the game should embrace Donald Ducks'' natural power.
Donald Duck is an Uber-Powerful Magic User in Kingdom Hearts 4.
Donald Duck may not appear like much, but is one of the most powerful magic users in Square Enix history. He can cast a Zettaflare spell, which had previously been used in all Square Enix titles, including once in Bravely Default and once in Final Fantasy 14.
While Bahamut''s Terraflare in Final Fantasy 14 (a massive move-down from Zettaflare) was still powerful enough to form a calamity and basically reboot a video game, Zettaflare is now used, but while not as dramatic, it is theoretically more powerful.
Donald Duck is the third user of Zettaflare, used during a battle with Terranort in Kingdom Hearts 3 to completely obliterate him. This doesn''t mean that Donald should go around and remove Zettaflares from the spell. Now, this doesn''t mean that Donald should go around with one in Kingdom Hearts 4 too soon and might pull away from the terribleness of that moment/the power of the spell.
If Donald can play Zettaflare, then he might have tons of secrets hidden up his head. In Kingdom Hearts 4s story, lore tidbits, actions, and more, Mickey and Donald seem to be aware of the threat, but Donald Duck is a powerful mage who can bend realities, defend his friends with a vast library of epic spells, and play a more serious role (silver maintaining his unique sense of humor).
Kingdom Hearts 4 is in development.