Yeah. As with everyone else, I'm gonna point out that, yeah. Missing the holiday season is DISASTEROUS on this one. It happened for the Wii version, but at the time, the Wii was the most popular console on the market BY FAR. With the current state of next gen consoles (none of them are doing terribly great, the PS4 is just doing less terrible at this moment), the holiday season is super important.
On top of that, though, the Gamecube adapter AND the smash Amiibos have had a release of November set already. That seems to indicate that Nintendo knows the release date for the Wii U version but is waiting until the 3DS version is released to reveal it, because, as several people have pointed out in other threads, they want to build the hype.