https://twitter.com/DisneyInfinity/status/631590096479895552/photo/1
So I stumbled upon this today and it's a tweet showing that they'll be hinting at what the ultimate unlock is for DI3.0 (In case you didn't know, the ultimate unlock is an item you unlock in the game as soon as you reach 100% with everything in the game and the item is basically related to something that would be the main focus on the sequel.For example, DI and DI2's ultimate unlock were items related to Star Wars which is ending up being featured in DI3... While this will only be a hint to it, take a closer look at the image. Keyhole.
Could this mean the ultimate unlock item in Disney Infinity 3.0 is a keyblade, which is a hint at Disney Infinity 4.0 having a Kingdom Hearts theme?