If this slides, it will set a bad precedent for all crowdfunds, all games. It means a crowdfunding developer can raise as much as $ 3 million and not have to follow through on their promises.
So, if you are one of the Wii U backers, it is imperative, your responsibility even, to sue Slightly Mad Studios, or at least threaten legal action.
Connect with the UK FSA (Financial Services Authority), they forced SMS to stop taking backers. Do what you have to to ensure doing things like this has consequences. Otherwise, other developers will do this to you again, and again.