KH is just anoher game. It has nothing whatsoever to do with FF apart from it having some of the characters there. Talk about confusion.
I originally heard Yoshitaka Kitase said he wouldn't mind doing a FFVII-2 but they wont be doing it.
As for why FFX got a sequel..look at it! It had the most open ended ending in history. And no one liked what happened with the Tidus part of the story (won't say for thos who haven't finished it).
FFVII has little to carry on from but I have discovered what they SHOULD continue to do..alas I cannot say since my idea would be ruined. But don not worry I might say it next post.