Someone has analyzed the video to death.
It's Jericho.
The 2nd promo has the clearly audible clip "I am the best in the world at what I do" in it.
The video is about taking back of what is rightfully his, and Jericho has been pounding on Twitter constantly about how everyone in the WWE has been ripping him off from CM Punk and now Miz. Specifically how X is the sign that CM Punk makes, and an X is marked over the word "Chris" on the book in the video.
Also, apparently Jericho has mentioned that not being in WWE '12 is a really sore spot for him as well, and some are saying that this is WWE's way of compensating him for missing out on those residuals, as well as giving him more ammunition with which to complain about on camera (kayfabe).
Likewise, there are the segments about a girl looking over at the boy's writings, and taking his answers, and the boy losing his ball, which the girl has now stolen, point to pretty much everything Jericho has been saying, as well as it being a little more than odd, that a modified Codebreaker, the old Lionsault, Miz ripping off Jericho's "No Country For Old Men" gimmick, and CM Punk using "Best In The World" have been on WWE tv recently, without Jericho attributed to them.
One person mentioned that the most prominent vignette was signaled on the Smackdown of the 25th, and the 25th letter of the alphabet is Y. And the return is signaled for the 2nd of January.
25 = Y, 2 = 2, and "J"January points to this.
It is also absolutely not the Undertaker, because the vignette is filled with biblical quotes about righteousness. Something that Taker has never been about. And I severely doubt it's Mordicai.
The blue, black and white hue of the videos almost perfectly indicate Jericho, as do almost all the references, the "best in the world" quotes especially, and the biblical, pseudo-philosophical slant to the entire video, as well as the obscure terminology used in the videos such as "punish the meek for their inequity"
It is absolutely, beyond a shadow of any doubt, Jericho.
Notice also how he has denied knowledge of SEEING the vignettes on his page, without actually coming right out and saying "No, I will not be there on that date, at all."
The obvious thinking is, seeing a CM Punk is really lacking a specific adversary at the moment, aside from Lauranitis, suggests that Jericho is going to be announced by Lauranitis himself on Janurary 2nd, to take on Punk at Wrestlemania.
However, Miz, who is also lacking a specific direction with his new, Jericho-rip-off persona right now, will probably also be added to the match as a three-way kind of thing, as the three of them are perfect to be at odds with each other right now.
Seriously, if this turns out to not be Jericho, I will eat my hat. And about a million things, both real and kayfabe pretty much scream, rather than simply point to Jericho.