I still think Nintendo should go with their strength. Mobile.
Create a powerful mobile platform, that is both a gaming system and a mobile phone, and enable it to work with a base station that offers additional features like motion controls, HDD-based storage, and optical media access/storage.
That way gamers can take their games mobile, but still have home game experiences. It wouldn't be as powerful as the Xbox One or the PS4, but it would be a unique experience that takes advantage of Nintendo's hardware strength and takes it took a new level.