Kingdom Hearts 4 is finally on its way, after stalling between the two for over a decade, the series is finally looking ahead to the future. Kingdom Hearts' distant past and present eras are all cleared up. The Lost Master Arc is coming, and everything it's bringing to the table is already beginning to appear.
Sora's aim has always been to find or rescue his pals in previous games. In Kingdom Hearts 4, Sora is instead the one who finds himself stuck and alone in the mysterious world of Quadratum. Whatever the Foretellers are planning will leave Sora with plenty to contend with.
Kairi's Time in Kingdom Hearts Hasn't Been Fruitful
The Kingdom Hearts fan base is all too familiar with Kairi, Sora's friend from the Destiny Islands and implied love interest. Kairi has spent most of the series either as a naivete or stuck in offscreen training. Before the Kingdom Hearts 3 ReMind DLC, Kairi was easy to pick out as the least relevant member of the Guardians of Light, and after Sora changed the timeline, she was the only one that died.
Even as other female Kingdom Hearts characters eclipsed her in impact, Kairi pushed for almost two games worth of story by extracting Sora's memories, Xion tied Roxas and Axel's stories together, and Master Aqua has too many feats to list. Sadly, Sora or Rikus could upstage Kairi once more in the Kingdom Hearts story.
The odds of Kairi contributing to Kingdom Hearts 4 are low.
Sora is now busy chasing unreality, and the majority of the named cast is attempting to save him. King Mickey is travelling to Scala ad Caelum to seek out information, and the other friendly faces are assisting wherever they can. Kairi decided that she needed further training, and sought Aqua for tutoring. However, her chances of doing so in Kingdom Hearts 4 are slim.
Kingdom Hearts 4 will focus on Sora's efforts in helping himself. The player will likely make new pals along the way. Kairi is once again unable to make up for previous failures, and the conclusion of KH3 implies that her relationship will continue to blossom.
Kingdom Hearts 4 is in the works.