Are we sure there's gonna be a new Smash direct before release? I mean..It would make sense, but I felt like Ridley would be revealed similar to Lucina and Robin or at the end of a general Nintendo direct.
Nah, I see him being revealed in a Stage Boss portion of a Smash Direct. As he shows off some more Stage Bosses, he says "Now, while we are still on the subject of stage bosses, let me show you the Pyrosphere stage from Metroid Other M. Please take a look."
Then a CGI trailer starts, and the fiery Smash logo comes up, and it shows a trailer that starts off heavily implying that Ridley is a boss, with Samus running around the stage in fear, with a humongous shadow chasing her.
The shadow is way too big to be a playable character, but then the figure comes closely to Samus, and as it does, the shadow shrinks, showing the shadow had an effect like this:
After the Shadow gets to a size where it isn't too big, but still large an menacing compared to Samus, the camera changes angles and shows us the purple figure.
RIDLEY SIZES UP THE COMPETITION!!!
After some Ridley gameplay, we go back to Sakurai, who says that he has been teasing this character for a while, and has implied it was a boss, but this was all because he knew how much the fans wanted him in, and he just wanted to have some fun with them.
He might also mention that in Brawl, he had Ridley as a boss, and he really liked him as a boss there. But this time, he had some player expectations he had to meet, so he made him a playable fighter.