Nintendo's software development support group seems to suggest the 'Project Café' name is more than just a rumour.

For the last few weeks as rumours about a successor the the Wii have been coming in the console has frequently been referred to as 'Project Café, the rumoured codename that has yet to be confirmed by Nintendo. As a company they don't comment on rumours so it is unlikely they will comment on whether or not the name is real the Nintendo software development support group seems to confirm it.

The support group, which can be viewed at https://www.warioworld.com/, allows developers to access materials and help while making games for a Nintendo console. While the site may look basic it is in fact an official Nintendo site and recently it has been noted that a certain URL may give an indication that the 'Project Café' rumour is correct.

Typically if you add any word to the end of the URL it leads to a 404 error, indicating that the web page doesn't exist. However, it has been noted that if you type in https://www.warioworld.com/cafe it takes you to the main site. This banner also uses the 'Café' title.

It is unlikely that the final name will have anything to do with the codename and even if this were the codename it shouldn't be used as any indication of what to expect. Don't forget the GameCube codename was Dolphin after all.