People thought it was september because of the eurogamer rumor, and I agree with tolu about november sounds fit for the reveal.
I'm fairly sure people were predicting September before the Eurogamer leak on the basis of it being 6 months(Sept->Mar) which is about the shortest time period Nintendo has ever had between announcement and release.
November doesn't really make any more sense than any other time at this point.
EDIT:
You really have no idea what mess at hw, sw and basically at everything at Nintendo an 8 month delay will cause.
Oh I'm perfectly aware it'd be a colossal issue.