The Kingdom Hearts series began its unlikely life as a mashup of both its Disney and Final Fantasy roots. The latest mainline release Kingdom Hearts 3 had a very noticeable lack of any characters until after its story DLC was released, though. While the move to further distinguish itself as a separate property makes sense, many fans worry that Kingdom Hearts may be abandoning an important part of its heritage if it leaves Final Fantasy behind going forward.
Kingdom Hearts has become one of the most popular franchises in gaming today, and a large part of that success came from its unlikely blending of the Disney and Final Fantasy worlds. Many fans felt spurned by Kingdom Hearts 3 leaving the latter out of its narrative. This likely stems from two different feelings about the presence of Final Fantasy characters in Kingdom Hearts: their inclusion can be both great fan service and helps serve the larger narrative in most of the games. Including the characters again in the story DLC ReMind was likely an attempt to assuage those fans.
Should Kingdom Hearts 4 Include Final Fantasy Characters?
Again, wanting to distinguish itself as a unique property is an understandable inclination for the Kingdom Hearts franchise, but for many, what makes the game's so unique is specifically because of its blending of Disney and Final Fantasy. Many moments that revolve around the characters admittedly do feel tacked on specifically as fan service. The struggle between Cloud and Sephiroth spilling over into another world was many fans' favorite side events in Kingdom Hearts 2, and since most Final Fantasy games don't receive sequels, Kingdom Hearts was a fun way to see characters like Squall again.
At other times, the Final Fantasy characters play pivotal roles in the overall story and in their appearances in some of the Disney worlds. Squall, Cid, and Yuffie were some of the first friends that Sora makes at the onset of their journey and reclaiming their world, Radiant Garden, from the grips of the Heartless was an emotional moment that impacted the overall narrative in a big way. So, these characters suddenly missing in Kingdom Hearts 3 impacted some fans' reception of the game. Even small roles in Disney worlds can create interesting blends of both of Kingdom Hearts 'parents' like Cloud and Zack both appearing in the world of Hercules, and the way their stories mimicked that of the original FF7.
Sometimes, the fan service and important story beats collided in big ways as well. The 1000 Heartless fight in KH2 was preceded by emotional moments that mixed interaction with Disney and Final Fantasy characters all alongside Sora. Fighting alongside Yuffie, Squall, Tifa, and Cloud was a culminating moment of the unlikely crossover as Sora looked to avenge Goofy with Mickey in a way that many fans of the series will never forget. And with Kingdom Hearts clearly bringing in elements from Versus 13, the lack of these characters in KH3 was jarring to many veteran fans.
Kingdom Hearts is still incorporating elements from Final Fantasy, so it seems odd to leave out some of the newer characters as well. Despite some mixed reactions to the game, FF15's Noctis is still one of the most popular heroes, and the classically moody Final Fantasy protagonists can be fun foils to the more happy-go-lucky Sora as evidenced by his affect on Cloud over the first two Kingdom Hearts games. Overall, it makes sense for Kingdom Hearts to want to chart its own path forward, but it shouldn't lose out on some of the characters that fans love and really helped shape Sora's early adventures.
Kingdom Hearts 4 isn't confirmed to be in development.