I hooe we get more unexpected reveals soon
...
Hmm...
I think it's possible we're being manipulated by Sakurai.
Pre-E3

Heralds the new Smash game, Inkling is the
most obvious pick for a Newcomer so they come first
E3
Sakurai's office decor evokes Donkey Kong with a rope ladder, barrels and a fern.

Introduces the new Echo Fighter concept,

and

are brought into the EF designation, but

is not.

A display that Sakurai is willing to change his mind regarding characters if demand is high enough
Post-E3
Widespread discussion and arguments start regarding what it means to be an Echo Fighter, arbitrary rules are put in place, as usual
August 8th

A hype-worthy 3rd party character, using his classic design. Likely did fairly well on the ballot.

Proves that third party characters can be Echo Fighters
Sakurai's office decor is fairly reminiscent of Skull Kid


Show how different Echo Fighters can be.

Solidifies the notion that characters are being selected from the ballot.
Post-8/8
Sakurai posts an image on his Twitter that is highly reminiscent of Golden Sun; as Sakurai says himself, he very rarely posts on Twitter.
People begin discussing characters that would have overlooked in the past (Isaac, Skull Kid), people come to expect more Hardcore-Fan Ballot picks as a result
Echo discussion becomes more refined, certain characters like Isabelle are considered nigh-guarantees for Echo-hood.
September 6/13th

A character generally popular with the Casual crowd (who nonetheless probably did well on the ballot) is revealed, everyone was expecting Isaac and/or Skull Kid. Not only that, but Isabelle is considered a unique Newcomer, and not an Echo.
Either Sakurai is playing us, or we're playing ourselves; either way we're getting played
hard. I'd like to think that after ~20 years and four Smash games, Sakurai has a decent idea of how fans react to announcements.
The tl;dr of this is that the previous 1st party reveals could have been setting up to make Isabelle more surprising.
...Actually... This gives me a thought...
A Prediction: We'll get Skull Kid and Isaac in the next Smash Direct.