In this thread, a person more powerful than every FF character

[Tavrobel]

Well his power comes from a key right? Which means, he needs to fight someone who uses a card key. The next stage in keyblade technology.

Keyblades aren't magnetic, which is how a card scanner works. I would argue that the next natural stage in Keyblades is Keycleavers. After Keycleavers, pocket-sized Keyblades. Of course, it would pretty redundant for a weapon that can be recalled instantly from the infinite backpack-hole dimension to become smaller and more compact, but they might one day create dampening fields to prevent recall (in case a Keyblade Civil War breaks out... again).

However, we do see what is the prototypical version of an anti-Heartless laser defense system in Hollow Bastion. If they can manipulate that system to read information rather than to emit an explosive blast, that would provide not only a way to identify people in the KHverse (which people seem to have real problems with), but also provide more potent defenses and exponential technological growth.

I'd especially like to have the ability to wield Four Keyblades although Sora's ability to wield to Keyblades has already been explained and wielding four wouldn't make sense... unless, he were dual-wielding two Light Realm Keyblades and two Dark Realm Keyblades (two would hover behind him like in Final Form).

KHII FM+ includes a fight with Roxas; Sora is able to borrow the power of both of Roxas' Keyblades after a successful Reaction Command. If you hack Final Form Sora into the fight against Roxas and complete the Reaction Command, he does wind up using four Keyblades.

Although according to this video, they don't do much other than when Roxas attacks; Sephiroth doesn't get hit by them at all. Ohh well!