1)
Anyone surprised that a game that involves buying toys to use in game would have "DLC" on the disc isn't paying attention. Skylanders has 'on disc dlc' in that you need the RFID with the toys to unlock the content.
2)
They're supplying the data for future toys in the system even if they haven't revealed what those toys are or will be. This can be because they haven't manufactured the toys yet, it could be that they're waiting for a movie/tv tie-in, or whatever. But given point 1, it doesn't make any sense to require any sort of download when they already know what they're going to do. Secondly, given that the toys won't be platform specific, they can't simply include the data with the toys without having to provide a copy of the data for every platform the game is for--that's a lot of wasted packaging and material. It'd only make sense to people who think that sort of thing is free and costs nothing.
So, in light of those things, this shouldn't come as a surprise to anyone whatsoever. Add in the justification that the target audience doesn't necessarily have internet access and you have the possibility of a lot of people who the product isn't designed for getting huffy over things that probably can't and shouldn't be done any other way.
So, before you get huffy about "on-disc DLC" on principle, consider that this specific product is NOT similiar to most other products, and the product it IS similiar to has On-disc DLC by design as well. Then if you still complain, explain how the product COULD be released without it.
3)
Someone WILL hack it--and I would bet good money that not only will there be 'leaks' about the unlocked content within a couple weeks of launch, some of those 'leaks' will involve people playing with that content as if they bought the content outright.
Just like Skylanders.