I don't think we'll be getting a general direct until December at the earliest, most likely January. The next direct will either be a short one to promote Pokemon Lets Go or a dedicated Smash direct. I think the latter will happen in October. Mostly because I want it to, but also because the longer they wait, the more time there is for stuff to potentially leak and spoil the reveals. Besides, if the Smash direct was held in early November, it would risk overshadowing Lets Go, which comes out on the 16th: people will likely be talking about the direct for several weeks afterwards. If held in late November, there's the problem of leaks and the fact that their marketing will be limited until then - they can't talk about Spirits, other stuff or show pictures of the full roster until they've been properly revealed.
The Smash direct will likely begin with a reveal trailer, most likely Incineroar. Then we'll have Sakurai discuss the character, perhaps reveal any remaining Pokemon and introduce the new Pokemon stage (still believe we might be getting a few more stages). Then, as last time, he'll move on to echoes, showing off Ken and maybe one other character at most. He'll then show a complete picture of the roster, which can allow him to segue into talking about how to unlock all the cast: Spirits. Sakurai will spend a good part of the direct talking about this mode, while briefly mentioning the returning single player modes at the end. Then we'll see any remaining new assists, the rest of the stages and online mode, which will also be discussed at length. Finally, after wrapping things up, we'll finish with a trailer teasing the first DLC character.
... At least that's how I think it'll go on the basis of the last direct. Probably going to be completely wrong, though.