Alright, time to post my theory on Echo Fighters:
tl;dr at the bottom
In Smash4, we got 2 "True" Echo Fighters, being
and
, no one can deny this fact, they just weren't given the name "Echo Fighter" then. Why do they have it now? Most likely to differentiate true clones from semi clones.
is more similar to
than
is to
, for example.
Smash 4 also did something interesting, in that Echo Fighters were revealed/hinted at alongside their franchise's newcomer:
was with
, and
was hinted at with
.
What this tells me, is that if a series has an echo fighter present in Smash, they'll reveal them in the same trailer as the actual newcomer.
It just makes sense, to be honest. We have one actual case of this with
, and a partial case with this with
.
So my theory is simple:
If a series in THIS Smash has a playable Echo Fighter, they'll be shown alongside any possible newcomer that they have, otherwise, they'll get a trailer like Daisy got, meaning no new character.
For example: If King K.Rool got in, and then three months down the line Dixie/Funky got shown off as an Echo... why? Why wouldn't they simply show off K.Rool and Dixie/Funky in the same trailer? So far, they have never done this in the past, and I see no reason for this change now.
Of course, then this holds true the other way around; if an echo fighter gets a Daisy-like trailer before any newcomers get shown for their series, then it's also logical to assume that that series won't be getting any new representatives. If the series was getting an actual new character, why would the Echo Fighter be shown off alone, not alongside their newcomer?
This brings to mind Geno, since Daisy got revealed, but considering Geno's status as a "3rd Party Mario Character", if he's in, it would not surprise me if he's part of a 'different' series altogether with a completely different icon than the Mushroom.
tl;dr: If a series is to have an Echo Fighter, they'll more likely than not be shown off in their actual Newcomer's trailer. If their series isn't to have an actual new character, they'll simply be shown off ala how Daisy was.
This is how Sakurai's done it twice in the past, and I can't see him changing it now. If Mario isn't to get a full-blown newcomer(Which I personally doubt), then Daisy being shown alone makes perfect sense, and if this is true, then it'll most likely hold true to any-other stand alone Echo reveals.