The Pokemon Scramble (Pokemon Rumble in the US) originally launched as a WiiWare title in 2009 and featured a realtime action-adventure mechanic that has Pokemon battling each other melee-style in dungeons, instead of the usual turn-based fighting. The sequel, called Pokemon Scramble U, will be making its way to the Japanese Wii U this Spring.
According to a recent CoroCoro magazine report, the Pokemon Scramble U that will launch on the Japanese Wii U this spring will be download-only, and will feature 4 player action. Additionally, the game will have all 649 breeds of Pokemon available for playing (although not all of them will be made available from the start. Perhaps some of them need to be unlocked in-game, or heaven forbid – bought as DLC.)