It’s yet to be officially confirmed by anyone whether this is some sort of teaser for an upcoming film or the next game. As well, WB Games has yet to make any kind of official statement. From TRMK:

We're hearing that this video is not anything seen before by those involved with creating Mortal Kombat 9 at WB Games. So if it is created by WB as a viral marketing clip, it was done with very few people involved or in the know. We're still waiting for an official comment at this time though.

It does appear to star Michael Jai White from the Spawn movie and more recently The Dark Knight. So it's either a very clever work of fakery or something more serious is being created.

TRMK is also reporting that this might be nothing more than just a rejected pitch for an R-Rated flick to Warner Brothers. Only time will tell, but if this in indeed a taste of what’s to come for the reboot of the film series, Mortal Kombat fans everywhere definitely have something to talk about for weeks to come. Let us know your thoughts in the forum.

Update 6/8: Actress Jeri Ryan, who played Sonya Blade in the Rebirth clip, confirmed via her Twitter account that this was a demo reel developed to sell the director's reboot vision of Mortal Kombat to WB. She says she has no knowledge of WB's reaction at this time. Thanks to forum member EnKompassedDra9on for bringing this to our attention.

Update 6/9: Crave Online has posted an exclusive interview with Matt Mullins, the actor who portrays Johnny Cage in the short film. From the article:

It has been really cool to see all of the buzz about the short. The truth is, the short is about showing a vision of what the next Mortal Kombat movie can be. I think it is a very well thought out concept that pays homage to the video game and its fans. The attention to detail and the little elements added will set this film apart from all the other films.

Thanks to Ed Boon's twitter post for the update!

Update 6/10: Collider has obtained an exclusive interview with the director of the short film, Kevin Tancharoen. Among several of the details revealed here, some include the plan to balance the series's mysticism and special powers with the real world and that the writer of Rebirth was Oren Uziel, a name revealed several months ago as the intended writer of the next Mortal Kombat movie. There is an audio transcript of the interview at the link above for further details.

Second update 6/10: On his Twitter, Ed Boon has finally stated his opinion of the video:

With the release of the teaser trailer for the new game, it's unknown what will happen with the "Rebirth" concept. However, Ed's comments indicate that while he liked it, the chances of it making to theaters are very very slim. If more surfaces, we'll keep you up to date.

Update: 6/14: IGN conducted an interview with the actor who plays Jax, Michael Jai White. Among other things, we learn that the film pitch was made about a month ago and was unintentionally leaked out. Another tidbit from the interview:

IGN: The character of Jax in the game was a little different from the version in the short. Can you talk about the decisions to ground it more in reality and change your character to be a police captain?

MJW: Well, I mean I think it goes along with the game to some degree. Now we played with some ideas on how to show that I still have those kinds of bionic arms --- robotic arms, with when my arm laying on the table to show reverberations. That Jax still has the metal arms. Now whether this is post-special forces, Jax is now captain of this force. But he's still a badass fighter, he's still has got the arms. It just wasn't much time to show that in the short.

Thanks goes to Casselman for this update.