Earlier today during the media briefing from Nintendo and DeNA president of Nintendo Mr. Iwata confirmed that their next dedicated hardware platform was in development:
As proof that Nintendo maintains strong enthusiasm for the dedicated game system business, let me confirm that Nintendo is currently developing a dedicated game platform with a brand-new concept under the development codename "NX." It is too early to elaborate on the details of this project, but we hope to share more information with you next year.
Source, with some speculation in the article: http://www.nintendolife.com/news/2015/03/nintendo_working_on_new_dedicated_game_platform_codenamed_nx
Before anyone says anything crazy, this does not mean the Wii U is dead. This could be the successor to the 3DS for all we know.