I don't think there is any need to repeat anybody when it has been said well. No it shouldn't, and it probably won't.
There is no subsystem that we know of in Kh3 that would make an ability system like this possible.
Instead, there are other options they will probably take.
1. KH2's ability system - Personally I think this is a bit too simple, but it has its positives. Skills unlock by completing tasks, story progression, and leveling, and that is the easiest way of approaching an ability system. It's clean cut without any complication.
Classic is always fine, yes, but considering every game after KH2 had systems that allowed for better customization for the player and a wider variety of skills to be used, KH3 should aim for a similar level of freedom but with better options and implementation.
2. Re:coded's stat matrix system - This is similar to a grid system found in Final Fantasy X and XII (maybe like XIII but that the Crystarium was linear for each paradigm so...eh) and imo much more appealing than a straightforward ability system. It also allows for freedom to "grow" Sora anyways you want. The problem with this is that obtaining abilities are restricted to how many points you have gained by defeating enemies to spend on them, and there will be a lot of filler that one has to progress through to get to a new skill. HP+, Magic+, Defense+, etc.