Just thought I'd point out another little observation going in Ridley's favor:
If you really put Ridley into the "stage boss" type of context, and then knowing that he, Samus, and the stage are based off of the Other M style, it's easy to notice that the way the shadow acts is nothing like the way Ridley acts in his Other M boss fight (or even his ssbb boss fight for that matter). For example, in Metroid: Other M, he doesn't even use grab attacks so often; and when he does, he doesn't grab Samus the same way that the shadow grabs Pikachu. I would think that if this was truly trying to represent a "cool" Ridley boss type "hazard" in the Other M style, then Sakurai would of had Ridley programmed to be much faster, use swooping attacks, quick overhead tail strikes, etc. Like in his Other M battle (go watch the battle with Ridley in Other M to see what I'm talking about). What we seemingly have seen in Smash 4 so far however, is a more 'player-paced' type of character (less intense) with a more traditional (less cinematic) grab and movement style (not to mention that the shadow does not seem pre-scripted and smooth like a boss at all). Granted we haven't seen so much yet with the short clip, but a surprising amount of info can still be deduced by simply using common sense and examples from the past like the brawl boss fight (along with your own gamer instinct).
There's a reason this thread has come so far. I understand the doubt some people have with Ridley, but more likely than not, Sakurai has heard the outcry for Ridley to be playable. From a business point of view, Ridley is an IMMENSELY popular character in the western markets. So much so, that the Japanese fan base is well aware of it. The western market is a much bigger, much more profitable market than the Japanese market, and as such it only makes sense to ensure that your most profitable market is pleased with the product; especially in the Wii U's situation. I would say that the big three 'market pleasers' are Mewtwo, K Rool, and Ridley. There's absolutely no logical reason why even all 3 of these characters should not be included. Hell, K Rool is topping charts on Japan lists as well, so what I would suggest is to try and not get so hung up on the Ridley detracting haters, the what ifs, and the over analyzing, and just use simple observation and common sense. It's not so hard to see that Sakurai gets his kicks from trolling and pleasing the audience. Take this comment for what you will, but I think Ridley has more than a fair shot at making the roster. Keep your chin up everyone.