"During the roundtable discussions there were such arguments about should we make it capable of being a standalone system or should we make it work only with the [base console] system," Nintendo president Satoru Iwata said to Gamasutra. It appears now that Nintendo has abandoned those plans according to their E3 press conference.
It wasn't only an idea Nintendo bounced around. After Wii U's big reveal at E3, many gamers had a similar idea when Nintendo chose not to reveal the console itself along with the controller. This lead to immediate confusion of their new product and message. Even after all the systems reveals Nintendo has gone through, they still managed to miss this glaring omission.