It makes perfect sense. He teased him as a boss, and then decided to let the hype run wild when everybody thought he was being teased as playable. The most damning evidence is the "enemy from Samus' past" thing on the Pyrosphere POTD. Why didn't he clarify like he did with all the other characters? Probably a combination of these things:
1) The hype was real, and hype sells games. Why kill that before launch?
2) Sakurai is a gigantic troll and thought it was hilarious.
3) Nintendo, for whatever the **** reason, didn't want anything more revealed about Ridley or the bosses.
Anyway, THE GAME IS OUT. Anybody who thinks more characters are coming is fooling themselves. We may see DLC eventually, but that's about it, and likely only as a way to hype new games as they release during the Wii U's console generation. I can just see that: Nintendo Direct announces release date for the new Star Fox game? Oh btw you can download Wolf in Smash now, $3.99. Pokemon get's it's first Wii U game? Here ya go, Mewtwo is $5.99.
If that type of thing doesn't happen, the roster is final.