Rabbids Rumble has been rated by the Australian Classification website, despite not actually being announced by Ubisoft yet. The listing does not reveal any information regarding release window, or launch platforms. It does say the game has "very mild crude humour." Sounds legit!
My guess is Rabbids Rumble is actually an N64 title designed to make use of the Rumble Pack. My second guess would be: it's a Wii U launch title and it will be officially revealed next month at 2012's E3.
What's your Rabbids Rumble theory?