I fail to see how this non-pattern equals a staple. This reminds me of Serebii forums. Every damn thing is a pattern that has to have significance.
Significance? No, but it's something expected considering they always do it. I predict that the next time Kingdom Hearts will be summoned a new method will be used, because that's what Square always does.
I think it's more like, the plot of each game calls for a different method so that the games don't turn stale.
My ideal here would be that the seven princesses are brought back again in regards to the forging of the X-blade. I could see Master Xehanort roaming around, stealing away the hearts of the seven princesses so that he has a large supply of pure hearts to use for the X-blade, or so that he has hearts of varying strength so that he can match up a light heart with a dark heart easier. Then he can just merge them with Vanitas or some other dark being that comes around to form the X-blade.
Well it's implied Master Xehanort already knew about the Princesses in Birth By Sleep, and he told Maleficent about them who in turn told Terra.
It's possible Master Xehanort will try to use a Princess of Heart to form the X-Blade, and it'll probably be Kairi since she's the only one who's a main character. Being a main character automatically makes her special, and anything that happens to her has more weight. Although I doubt this would happen.
The X-Blade is the only one of the three methods I expect to be used in the future again. That doesn't mean I'll be surprised if Master Xehanort uses some new method to obtain Kingdom Hearts, but the X-Blade has the best chance of returning.
I just don't see the Princesses of Heart coming back in any important role since they've been incredibly downplayed after Kingdom Hearts I. Birth By Sleep only mentioned them to reference the importance they would have in Kingdom Hearts I.
Maybe Master Xehanort plunges the Realm of Light into darkness, and the Princesses all gather out of instinct or something like that. Maybe they open the road for Sora to fight Xehanort or something, but I'd just like them to do something.
The original characters in Kingdom Hearts are beginning to overshadow the Disney characters. I don't mean people like Terra, Aqua, or Ven. I mean the way the Organization was implemented into the story, and the fact that we're once again seeing those black coats as part of the new Organization.