I have a question for you all, that maybe you can answer. In Super Smash bros. Brawl, did any franchise ever get more representation through assist trophies then playable characters? I ask because right now, there are 3 confirmed metroid assist trophies; Metroid(NOT a pet), Dark Samus and Mother Brain., but we only have 2 playable reps, that we know of. If other franchises have had this happen then I will simply ignore it, but if there thus far has been always equal representation between assist trophies and playable characters, does that mean it already confirmed one more?
Brawl had the following assist trophies:
Andross (Starfox)
Barbara the Bat (Band Brothers)
Devil (Devil World)
Dr. Wright (Sim City)
Excitebike (Excitebike)
Gray Fox (Metal Gear)
Hammer Bro (Mario Bros.)
Helirin (Kuru Kuru Kururin)
Infantry and Tanks (Advance Wars)
Isaac (Golden Sun)
Jeff (Earthbound)
Jill and Drill Dozer (Drill Dozer)
Kat & Ana (Warioware)
Knuckle Joe (Kirby)
Lakitu (Mario Bros.)
Little Mac (Punch Out!)
Lyn (Fire Emblem: Rekka no Ken)
Metroid (Metroid)
Nintendogs (Nintendogs)
Ray MK II (Custom Robo)
Mr. Resetti (Animal Crossing)
Saki Amamiya (Sin and Punishment)
Samurai Goroh (F-Zero)
Shadow the Hedgehog (Sonic Series)
Stafy/Starfy (Stafy)
Tingle (Legend of Zelda)
Waluigi (Mario Bros.; Spin-offs)
So in response to your first question, going off this list, the answer is no.
In Brawl, no franchise that had a playable character had more assist trophies from their franchise than playable characters. Although it is seemingly something minor, it is still something to note considering that as you said, we have 3 Metroid Assist Trophies in Smash 4 with only 2 confirmed Metroid characters, which would be odd given that such a thing didn't occur in Brawl.
Worst case scenario, Sakurai decided to change his mind and provide more assist trophies than playable characters from certain franchises this time around, but who knows?
Good catch though, I certainly hadn't thought of this whole Playable/AT situation at all.
EDIT: Half-