Everyone knows Zelda is the first party IP they need on the Wii U. A Metroid reboot that isn't horrible *cough* Other M *cough* will be a great filler-title, but it won't sell that much hardware.
It is perplexing, though, that Nintendo would market the Wii U toward hardcore gamers, and then deliver Mario and Smash Bros. There's nothing wrong with these games, of course, but they don't particularly appeal to hardcore gamers, either. Among Nintendo's IP, only Zelda and Metroid have a "hardcore" fanbase niche, but Metroid is much weaker than Zelda, particularly in Japan.
All in all, Nintendo just needs some time to think about what they want to do with Metroid after Other M, and with a 10-year console cycle they've got plenty.







