Are you implying that Rayman Legends would magically improve WiiU sales?
Now, don't get me wrong, it's going to be a great game, no doubt, but Rayman Origins did not sell in zillions and certainly wasn't a system seller. It's on the PSVita and it doesn't seem like it's pushing the system forward - if you're expecting Legends to push the WiiU, you've got another thing coming.
Not many people gave a cluck about Rayman Origins or Legends and now that Legends was both delayed and announced to be Multiplatform, even less people will care for the WiiU version when PS3/360 versions will be readily available, nullifying the need to buy a new system just to play this game.
What the WiiU needs to triumph in Japan are JRPG's, what it needs to triumph in the West are core games, what it needs to triumph on a global scale are Mario, Zelda, Metroid and Pokemon. If those three conditions are met, we have another successful generation for Nintendo. If not, the sales will remain lackluster.