A score for Ridley's chances? Hmm...
Well, the last time we officially rated him, I gave him a 45% score. Basically I thought it could go either way, but slightly leaning towards him just being a boss. After that, I really started thinking about Ridley, and I realized that what we've seen and what we've been told just doesn't add up. Sakurai de-confirms characters quickly and simply, and makes it very clear when a character is playable and when they're not (Skull Kid and Ashley are good examples of this). He likes avoiding creating unnecessary confusion. I would think that after Ridley was teased, Sakurai would probably have noticed all the debate the Direct caused, and would have tried to correct it shortly afterwards by officially revealing Ridley as a boss. Despite that, Ridley has yet to be acknowledged once. On the other side of things, Sakurai has a tendency to tease characters that do end up being playable and likes making indirect references to them (Palutena and Little Mac). Ridley's teasing matches what we've seen with newcomers much more than it does the random de-confirmations we've seen before. So how Ridley has been treated as a reveal doesn't make sense if he is a boss.
Then there's the issue of Ridley himself, since we got a brief glimpse of him in the Direct. As a number of shadow analyses have pointed out, Ridley isn't exactly huge. He seems to be large, but his size seems to match that of a large playable character, rather than a boss. Why would they make Ridley so small if he's a boss? And then there's the matter of how "boss" Ridley actually acts. Bosses in Smash, for the most part, have a fairly basic script they follow: stand still on part of the stage for a moment to let people attack them (usually this is the left or right of the stage), attack, or move to another part of the stage while attacking. All of this is done fairly quickly. Now, if the Yellow Devil is any indication, this basic pattern for bosses remains the same in this game. But if we look at how Ridley acted in the Direct, it's just odd: he slowly flies in from the right of the stage, stops in the middle, appears to do nothing, then slowly flies to the the left end of the stage, and then makes an immediate turn and starts slowly flying back towards the middle. Within all that time he's there, there is no indication that Ridley ever made any offensive movements. In other words, if Ridley is a boss, he's a very slow moving boss that hovers over the stage and does absolutely nothing to harm the players within a time frame of at least ten seconds. This not only fails to match up with any kind of boss we've seen in Smash before, but it's really just a bad boss design and an inaccurate portrayal of Ridley.
Basically, while it was suggested that Ridley was a boss, almost nothing about how Ridley was teased or how he actually acts matches up with this suggestion. And considering how Ridley is a highly requested newcomer and how Sakurai is really quite the troll, I think I'd seriously give Ridley a 75% chance of being playable at this point. Sakurai may have suggested that Ridley is a boss, but frankly, nothing else does.