At first glance, one might assume it's footage from the new, possibly derailed Mortal Kombat movie. Another possibility, given the video's proximity to E3 and its introductory nature, is that this is a tease for the next Mortal Kombat game. Furthermore, the name of the newly created YouTube account is MortalKombatRebirth, which sounds like a perfectly suitable title for a new entry in the series. A third and altogether frightening possibility: This is all a prelude to a new movie / game tie-in.
We know Warner Bros. is interested in the franchise, so it's safe to assume something is on the horizon. We've contacted WBIE for more info. One way or another, it seems likely we'll hear more by next week.
Update: Latino Review claims that it's a test video directed by Kevin Tancharoen, and offers a near-complete list of the featured cast.
Update 2: Actress Jeri Ryan, seen in the short playing Sonya Blade, offered further comment about the project on Twitter. "It's not a game trailer," Ryan said. "Actually was made for the director to sell WB on his vision for a reimagined MK film." She said she had "No idea yet what WB's reaction to it was."