Well at first I was very excited, until I realized how strange it was for him to be hinting so clearly at Ridley, then the stage hazard idea kicked in.
But reading it again, like I was saying before, it could ALSO just as well be read as Sakurai pointing out that, because this is the area you encounter Ridley in Other M, it's as though he could appear at any moment. Something like that is much more in line with what Sakurai typically does. A little blurb of the history associated with the update, y'know. Reading it like that, I think, solves all the confusion.
SAKURAI HAS HUMBLED ME GREATLY, I'm no where near saying I feel this puts Ridley closer to being confirmed, but I do remain a little hopeful.
Also you can't really put a time frame on Ridley's confirmation. We just have to look at each image of the Pyrosphere individually as Sakurai gives them to us, which should at most be bi-weekly. We'll surely get another character in less than a month, but for who it may be is anyone's guess really. The "at any moment" really shouldn't lead you to believe he's going to be confirmed soon. I am pretty confident we will see him before release if he is indeed playable. Maybe next E3?
By the way, if Ridley doesn't get in, I think I'll suddenly become a supporter of DLC, lol.