Game France has listed the Wii U with a release date of Novemeber 15, 2012.
While Nintendo has yet to announce an actual release date, Novemeber 15 does seem to be a safe bet. Publishers have already begun listing it’s games to come out around that time so it’s very likely to be true.
The only thing that could hold this rumor back is the recent (other) rumor which stated Nintendo having difficulty with supplying enough units in Europe in time for the holidays.
Hopefully all these rumors will be put to rest when Nintendo announces the full details next month.
Source Game France via Gamekyo