The DLC is finally dated.
http://www.nintendoworldreport.com/news/47462/mario--rabbids-kingdom-battle-donkey-kong-adventure-taking-off-june-26
Ubisoft has finally unleashed the long awaited DLC for Mario + Rabbids Kingdom Battle featuring Donkey Kong.
The Donkey Kong Adventure pack will be available for individual purchase on June 26, with holders of the season pass getting the pack on June 25. A Cranky Rabbid - or at least, a Rabbid with a long beard - appears to join DK and Rabbid Peach in the trailer shown below. Four brand new environments are promised for the expansion.