I really think it depends on your money situation, whether or not you've played CoM, and whether or not you think it's worth it to buy another version of a game you already have to get some new things or if you want to wait for the next official game.
If you don't really have the money to buy it, you can always watch everything on youtube a week after it's release. I'd say it's worth it, but I trudged through CoM on my gameboy, and the only reason that game was lacking was because it was on the gameboy. I'm really excited to use a controller for that game.
Also, if you're really die-hard desperate to find out more info for yourself, then you would probably want to pick this up. On the other hand, if you're fine with just reading about it while waiting for KH3, then I'd say no.
It's all about personal preferance, and how big your money tree is.