Polokus is a normal guy.(NOTE: Bubble Dreamer = Polokus) He's just a completely normal dude having some crazy dreams. In Rayman Origins, he's often seen with a pipe, so maybe he does some kind of drug in real life, which could be a cause for such crazy dreams. This gives Rayman a strange place, though. In R2, it is said that Rayman was not created by Polokus. So either A, Polokus DID dream up Rayman but also dreamt up that he didn't dream up Rayman, B, Rayman is a psychologist or other person that could really get into your head, or C, Rayman is performing Inception. The similarities between the Rabbids "BWAAAAAAGH" and the "BWOOOOOONG" from the Inception trailer makes it seem like Ubisoft was hinting at this.
Mr. Dark will be given the Knight of Cerebus treatment.It would be an interesting way to show the character, really.
Mr. Dark will turn out to be a Psycho Prototype of Rayman, who rebelled against his creator for some reason.I can't be the only one who thought of that. If they're going to give an origin to the character of Mr. Dark as well, this is the most obvious road. The dev team could have predicted this and decided to take a more unexpected approach for the sake of a twist, however.
There will be more playable characters.Which may include Ly, Polokus, and Mr. Dark being playable, likely as unlockables, though.
The Magician was Mr. Dark all along.Why was the Magician so sinister looking in the trailer? Think about it. They wear similar clothing, and outside of the cutscenes and secret levels in the first Rayman, you barely see the Magician at all. He also knew a lot about Mr. Dark stealing the Great Protoon and fighting Betilla, yet the Magician is nowhere to be see when all of it went down (not counting the Rayman Junior games) It's possible that he pulls a Face-Heel Turn (or was Evil All Along) and becomes Mr. Dark, and nobody else realizes who he really is. He uses his Magician persona to spy on Rayman and his friends without any suspicion, and sets up mooks and traps in advance.
How does The Magician get the Electoons he trades for Lums?The Lums are more important than the Electoons for powering The Magician's machinery. He can trade Electoons because he helped cage them up in the first place.
The explanation for the inexplicable dance number.Notice how the Magician loses his hat right beforehand, and upon realising this, he dances. He was trying to make it seem as if he had somehow been possessed or controlled by his hat, and was dancing in celebration at being freed! That's why everyone joins in; they all believe him! And then he makes a break for it.
The Origins timeline (Origins and Legends as of the posting of this WMG) will end in Mr. Dark being the final boss in a future game.