Birth by Sleep Birth By Sleep to KH3

A sequel to the prequel would either be another prequel or the first KH itself. Sequels aren't as possible, but prequels are definitely plausible.

 

Mostly games do end in 3.

It is rare to have a 7th.

 

It is rarer to even go beyond a fourth of fifth. FF does not count, as every game has a different storyline, world, characters, etc. (with some notable exceptions) Most games that do go beyond a fourth or fifth usually have the same plot but told in a different way.

Of course, there are very rare exceptions.

 

WEll you get 3 because of a Trillogy, it's just something popular in Media.

And If you think about it, all these prequels are connected to the actual story of Kingdom Hearts itself, they can't really make more prequels or sequels if all the Heartless are defeated sinc eit started with the Heartless, it has to end with them.

 

Sora, Riku, Kairi
Sora, Donald, Goofy
Mickey, Donald, Goofy
Terra, Aqua, Ven
Marluxia, Larxene, Axel
Vexen, Lexaeus, Zexion
DiZ, Riku, Naminé
Heartless, Nobody, Unbirth
Heart, Body, Soul
Light, Darkness, Dawn
Trinity Limits
KH1, CoM, KH2
BBS, 358/2 Days, Coded
KH1, KH2, KH3