X360 (an Xbox 360 magazine from UK) has an article along with new pics and info of the upcoming: Mortal Kombat vs DC Universe.

The magazine introduces 2 new characters: Sonya Blade (from Mortal Kombat) and The Flash (from DC). Flash looking like like the classic Flash we all know (no details on who is behind the mask), Sonya looking to be a mix between her MK4/Deadly Alliance looks (beret, long hair/ponytail, white/short shirt, black pants/gloves).

The new pics in the magazine also reveal some details:
-Small traces of blood (for the ones still worried about "no blood")
-Breakable aspects in the characters costumes (Scorpion's mask being broke by a punch in the face by Superman, revealing the skull under it)
-Superman using his eyes-lasers.
-Flash doing a "spin dash" (ala Kabal)
-Scorpion using Teleport Punch

Among other things...
Scans are not allowed, neither links..so no pics here..hehehe..

Also, the unofficial list of confirmed characters seems o be:

DC Universe
Batman
Superman
Robin (Tim Drake)
Wonder Woman
Flash
Green Lantern
Black Canary
Hawkman
Powergirl

Mortal Kombat
Sub-Zero
Scorpion
Kabal
Sonya
Jax
Raiden
Kitana

There seems to be at least 20 characters in all, and the contracts seems to be for 2 games..so who knows..
There also plans for downloadable content as in more characters and stages..

There seems to be a collector's edition in the works (as Midway was polling a few weeks ago about what would you like to see on it: a comic, artbook, etc) and there also seems to be a comic in the works; acordding to The Realm of Mortal Kombat website (which were one of the firsts to break the whole MK vs DC rumor, along with the GAF poster):