Again as ever, you'll be able to watch the Direct right here on Joystiq, and we'll have all the big news up on the site as it spills out across the stream.
As for what to expect... well, this will be Nintendo's first Direct not specific to a single game since it announced the "New 3DS" in the Japan-only stream back in late August. It's just speculation, but maybe we'll hear more about the New 3DS and details of its arrival in the West. That would certainly be nice.
But if you're a Nintendo Direct connoisseur, you'll know as we do that it's folly to try and predict what the big N will show. Unless it's Smash-related and leaked beforehand, that is. You're on safer ground then, just about.