Probably not one in September. We already got one or two surprise ones this month. I am thinking end of October or November for the next one. They'll talk about Mario Cats and Donkey Kong fur in the next one. Also the leaked bundle with NSMBU & Luigi U and price of Wii Fit U.
Doesn't make too much sense talking about 2014 games as that just takes attention away from their Q4 portfolio.