It's similar to a theory I had after King K Rool's reveal. I noticed the order of the reveals matched the characters appearance in gaming, and excluded Inkling as she didn't have a proper trailer reveal, but instead used to promote the game as a whole. My feeling was Sakurai wanted this to be the Ultimate Smash game for every fan, new and old, and so balanced the prominent potential picks with where they originated. My thoughts were:
NES: Ridley, Simon
SNES: King K Rool, Geno
N64: Banjo & Kazooie, Skull Kid
Gamecube/Advance: Isaac, Chorus Kids
Wii/Wii U (3DS): Incineroar (& Inkling)
Making 10 unique newcomers total. Of course, it wasn't that great--I still felt like 10 might be too many newcomers, and I included Chorus Kids as a non-ballot Sakurai pick, despite almost exclusively focusing on the polls (my bias) and lining them up with Verg's claims. As well as it was difficult to come up with characters from the Gamecube era (a system I never owned, bias). And I was fudging things in the Gamecube-Wii U era to make things fit, whether to include handhelds or not, and if so, how. Overall, I didn't like my theory, so I never did anything with it (so I'm in no ways taking credit for "theories" I never posted about to begin with, just sharing my previous thought process). And then Isabelle came and screwed a theory that wasn't that good to begin with. Still, I liked the idea of it and felt it was the most inclusive way of including many fan favorites in the roster, and it's still possible the order isn't a real pattern, but balancing newcomers by generation still could be.
Still, the idea that the order of reveals being the order of their appearance still stands with the facts as they are now. My only personal issues are, I think they would choose to market characters in an order that will maximize profits, not follow a specific pattern and it may just be a coincidence as of yet. As well as with Isabelle, skipping three console generations of potential newcomers is a bummer. But those are biased criticisms, rather than factual.