Just another random theory slighty related to the blog theory.
So far, they made blog posts for 1 or 2 new stages each month (this includes new battlefield/final destination), along with some posts about returning stages.
The point is that they ran out of new stages to show.
If the 108 stages thing is true, there are still 5 stages to show, and if they make a post about 2 new stages each month from now, 2 stages in october, 2 in november, 1 in december during the last week, it would fit perfectly.
Does this mean that they will announce a direct soon? Maybe the second or third week of october?
I know that Sakurai said to not expect too many newcomer announcements soon, but it would make a lot of sense to get a direct this month.
It can even be the final Smash direct, who knows.
They have a lot of material yet to show on the blog, so I think the blog will continue being updated even after the game launches (because of this, I doubt they will show EVERYTHING in the blog before announcing the next Smash Direct).
If this is true, it's possible that they will keep one last character (in total secret, they'll say that the roster is final) to be announced during a regular direct in late november, or they will just reveal all the characters in october and that's it... or maybe in november they will announce DLCs....
I don't expect 5 characters during the next Smash Direct, there will be less, for sure.
Also I think it's possible that from now they will show 2 characters at week instead of 3, with some exceptions.
There is also the possibility that they will just stop showing new stages, but I think it would be a bad choice to promote the game, especially if you actually still have 5 stages to show.