Here is something to chew about Elma fans worried she may never have another opportunity to ever be playable in Smash Bros. Think about Dark Samus. Dark Samus's time more or less to be added as a playable character was with Brawl. By the time Smash 4 was released, Prime 3 was already seven years old. Fans of the character were even pleasantly surprised by the fact the character got an Assist Trophy. Yet it was probably the existence of said Assist Trophy that even made Sakurai aware of the character. Prime 3 coming out after Brawl in Japan was likely the cause for this, and Sakurai likely wanted to throw a bone to the only other Metroid game to be released after Brawl (most of Smash 4's Metroid content was derived from either past Smash Bros. games or Other M).
A year ago, who would have thought that out of Donkey Kong, Metroid, Kirby, and Star Fox, that Metroid would be the first series to reach four playable characters in Smash Bros.? When Sakurai had already said Ridley was too big? When Dark Samus was from a game over ten years and likely never coming back? When Sylux's break out role title (likely Prime 4) did not even have a release date? When Dixie Kong, Bandanna Dee, and Krystal each individually seemed to have more support than both Dark Samus and Sylux combined?
And now look at the roster. Both Ridley and Dark Samus are playable. I would never have believed that this was a plausible scenario a year ago if you told me.