Have you considered.... maybe the big surprise at the end if Spirits Mode?
I personally feel like they front loaded the reveals this time instead of doing it the opposite way.
We got "EVERYONE IS HERE!" which was a huge deal.
We got Ridley, K.Rool and Isabelle, which were all huge deals in their own right.
I'm not going to hold this game to any prior 'patterns' of previous Smash games, because this game is special.
We've never had EVERYONE back.
We've never had almost EVERY stage back.
We've never had over 800 songs.
Like, I'm potentially looking ahead, while you're looking in the past for patterns here.
Depending on the magnitude of the mode, Spirits could certainly be a large reveal.
What has been an increasingly popular request in the time between Sm4sh (even shortly after release) and Ultimate?
A sequel to Subspace Emissary.
Despite it's flaws, it's looked back on fondly by many fans. Maybe it's just nostalgia, but I wouldn't be surprised if casual and hardcore fans alike have expressed a lot of interest in it, be it on Twitter, 4chan, fan forums, etc. I don't know what the Japanese thought of SSE, but if it's anything like how it's regarded here, I'd say that Sakurai and the team are well aware of the demand.
A large story mode in a game of this caliber would be
huge, especially if it was the last reveal. No single character could beat that out in terms of sheer hype inducement within the community and at large.
Spirits being a sequel/successor to SSE is one of the only reveals that could match "Everyone is Here!" and part of me feels like Sakurai and his team are currently banking on that.
My prediction: The final Smash Direct will take place somewhere between mid-October to mid-November. It will contain our remaining characters (Incineroar, Ken, maybe another echo and the SE character), expand on single player modes, stage builder, etc., reveal Spirits mode in all of it's glory, and end with the reveal of DLC (this might be the SE character assuming box theory is true)