I don't actually think Ridley will be playable in Smash 4, but I'm not a fan of the way Sakurai has handled the situation either. He made it clear when other characters weren't going to be in the game, but whether he intended to or not, he has been stringing Ridley fans along for ages now. Even if that 'other playable boss characters appear' wasn't him trolling, he must have noticed that it had just made Ridley supporters even more thirsty, and should have shut it down shortly afterwards.
I think, Sakurai knows exactly what he's doing to Ridley fans.