Some users got brain training in the past as a gift from nintendo. They can use that to install as Haxchi. ( for free ).Just found out about the 11.3 update for the 3ds.
Good thing the 3ds (if it's below 11.3) can be hacked with an offline entry point (soundhax).
That's not true for haxchi on the WiiU. To use haxchi (or the even more handy CBHC) you need to be able to BUY (if you heard about the latest user who bricked, you'll know why I put it in caps for good measure) a suitable DS game off the eShop. To access the eShop, you need to be on the lastest firmware (EDIT: except if there's a working workaround like "NNU patcher" after the hypothetical new firmware is out). If a firmware above the current (5.5.1) comes out in the coming weeks, you're screwed.
Now, before 11.3, we could just assume Nintendo would let go last gen consoles and not bother to patch holes.
But now, there's astrongmild cyclical indication the WiiU could be the next in line after the 3DS. EDIT: THE INDICATION BEING THE 3DS BEING UPDATED WITH SPECIFIC PATCHES TO THWART HACKING, AS A SYMPTOM OF NINTENDO'S CURRENT ATTITUDE, NO REAL SOURCES OR RUMORS, THIS IS 100% PURE UNADULTERATED SPECULATION
Be safe and haxchi your Wii U today, then set up the DNS to block upadtes (or disable networking altogether if you don't play online).
Newer buyers are out of luck and have to purchase a valid compatible game, but it never hurts to check if you are lucky and this download is waiting for you but never installed it in the past.