In reference to Epic Mickey 2: The Power of Two on the Wii U, Warren Spector has said they didn’t “keep [the game] secret as long as you might think”, explaining that:
We put together a proposal that got kicked around at Disney, and Nintendo for long time. At the end of the day we probably seriously started working on it about 6 months ago. I just have to be clear about the one thing.
This is a surprisingly short amount of time, and makes a lot of sense considering how the earliest rumours of the game were repeatedly squashed. It’ll be interesting to see how the short turn-around time affects the final product of the port.