In no way, shape, or form am I saying you're wrong, but, we could totally be looking too far deep into this and Rids could simply just end up being a stage hazard. While Sakurai definitely cares more about the fans wants than some salty fans may think, that still doesn't prevent him from doing his own thing. On the other hand, popularity isn't big enough to grant you access in Smash. Wasn't Yellow Devil, Dark Emperor and Metal Face all implied/teased as a stage boss before finally being revealed? While you can say that Ridley is more popular, it doesn't change the fact that they (at least Metal Face in this scenario) are in the same boat as Ridley.
However, this doesn't diminish Ridley's chances that he could still be playable. Personally, I think we might finally find out Ridley's fate this Thursday. Also, it could simply be that Sakurai is out-of-touch with the fanbase (in terms of Ridley), as he believes hyping a stage hazard is cool. Not saying it's true, but he hyped Metal Face (who is not as popular as Ridley mind you), but I wouldn't put it pass him. Simply put: Nobody can or will ever predict Sakurai's moves as his way of thinking is different from ours. Mentioning that Sakurai doesn't like giving false hype is true, but what is also true is that he has been teasing Ridley as a stage boss, no matter how ambiguous it was. While Ridley can still be playable, he was teased as a boss, so therefore if he ended up playable, Sakurai would have created false hype (though because it's Ridley - a character many want, nobody would care).
All in all, we'll just have to wait, but I have a feeling Ridley will finally be revealed. So I say your strength in your argument is that you question why would Sakurai go through so much to hide Ridley and not have a payoff. It seems odd, and almost seems like he's singling only Ridley out. On the other hand, you could simply just looking too much into it, and might have to take it at face value. Only time will tell, and I hope that you don't get disappointed on the chance that Ridley ends up as only a boss; likewise, express your happiness and joy for Ridley's inclusion if that is his role.