From the beginning, Kingdom Hearts was built on a crossover between Disney and Square Enix. Final Fantasy and animated Disney characters were interwoven throughout the game, appearing in all manner of locations. Final Fantasy 7's Cloud Strife and Sephiroth showed up in Hercules' Olympus Coliseum, while Squall from Final Fantasy 8 and part of the FF7 party appeared alongside Huey, Dewey, and Louie, Merlin, and the Fairy Godmother in Traverse Town. It was a strange concept, but somehow worked, and propelled Kingdom Hearts to massive success.
However, as the series continued, what these two components brought to the crossover changed. On Disney's end, live-action and Pixar movies also integrated into the series much like their 2D predecessors. Square Enix provided the occasional new crossover like The World Ends With You in Kingdom Hearts: Dream Drop Distance, but its existing properties took a back seat. With the ever-growing number of original Kingdom Hearts characters, it was deemed that Final Fantasy was no longer an essential part of Kingdom Hearts crossover nature, and the old FF cast was marginalized. There’s no sign that this will change, but there may be other ways to bring Kingdom Hearts and Final Fantasy together.
Sora Can Follow Final Fantasy Wherever It Goes
The contents of the Super Smash Bros. Ultimate Fighters Passes need little introduction. Not counting Piranha Plant, a whopping eleven characters from throughout the video game industry were added to the game. Both Passes were filled with surprises, but the second one held major boons for Square Enix fans. Sephiroth was added halfway through Fighters Pass 2, and he brought with him the CGI trailer Cloud never got, a stage that remade the ending of Final Fantasy 7, and many songs that fans felt were missing from Cloud’s Smash 4 addition. Even though it felt odd to some that Final Fantasy 7 got two representatives, FF7 fans were too busy celebrating to care.
That sentiment was repeated when Kingdom Hearts' own Sora closed out Super Smash Bros. Ultimate’s DLC. It felt fitting to have a character predicated on crossovers close out the largest gaming crossover thus far. Not only that, but Sora was finally reunited with Cloud and Sephiroth, who both featured prominently in Kingdom Hearts’ early days before disappearing almost entirely. Sephiroth is an iconic bonus boss in Kingdom Hearts 1 and 2, and is also the focus of a subplot involving the light and darkness in Cloud's heart. This story thread has been left hanging to the chagrin of fans, but they got the chance to act out the ending themselves in Smash. This reuniting of franchises felt almost poetic, and Square Enix should try to emulate it itself.
Final Fantasy Has Room for Kingdom Hearts Cameos
If Square Enix can make use of the parts of Kingdom Hearts that they own, or reach some form of agreement with Disney, then Sora and friends could visit other Square Enix games. Most notably, Sora could show up in later parts of Final Fantasy 7 Remake. This would probably be limited to the VR combat trials, but it would still be fun to have Sora reunited with the FF7 party in a context where they could talk. The FF7 Remake trilogy already seems to be dealing with alternate timelines, so a simulated incursion from another world isn't too far-fetched. Besides, Dirge of Cerberus' Deepground has already been integrated into the story, and Crisis Core's Genesis Rhapsodos is likely to follow. A Sora cameo may not even be the most ridiculous sight by the time the series concludes.
There are other avenues for Sora to travel on as well. Final Fantasy 14 comes to mind first, as the MMO already has a pattern of other Final Fantasy protagonists falling through portals into Eorzea. Considering that NieR: Automata got an entire raid series devoted to itself, having Sora appear for a quest similar to the Monster Hunter Rathalos event wouldn't be out of line. And, given the series’ existing gameplay ties, Dissidia Final Fantasy fans would be happy to have Sora in the next big Dissidia project. Sora appearing in other Final Fantasy projects may be hit or miss, but it would still be nice to see him, even if it's just a small reference like a Keyblade weapon. Smash Bros. has proven that legal red tape isn't as big of a concern for Kingdom Hearts cameos as many thought, so Square Enix should take a chance on expanding its crossover franchise a bit more.