Basically I see a few outcomes happening:
1. Character Trailer next week: 1 Unique or a Unique and Echo fighter. Thats it. Leaves space for a final direct in November and likely satisfies us for the month. It could hurt the box theory's claim of only 2 more characters for base, simply because the previous Smash directs usually have 2 unique character reveals, however that trend may not continue, who knows.
2. Final Smash Direct next week: Sakurai tells us this is it, reveals everything. Boom, speculation is done until DLC or some sort of miraculous surprise that he never told us about anyway. Will kill or confirm the box theory.
3. Smash Direct next week, but it announces something else in November: Reveals a few characters, possibly saving another for later. Would probably kill the box theory, as 1 character each direct (1 being an echo) makes little sense, imo.
I'm inclined to think its not 2, only because Sakurai's comments last week specify that the "rate" will slow, meaning that you have to have more than 1 event to reveal characters and "slow down the rate significantly". If the final direct is next week, there's no reason to make that comment. At least 1 and 3 allow for more information.