Definitely. While I myself have no problem with the name, I have a feeling the name and the design of the system combined would have a negative effect on sales. I could already imagine people having trouble trying to tell the difference between the Wii and the WiiU.
However, if they were to change either the design or the name, I feel it would be better off. Although, this late in development I'd imagine changing the name would be easier then changing the design, so it'd be better if they'd change the name. Anything without Wii in the title would be better.