A little over a week ago, NetherRealm confirmed that Lobo would be the first character introduced to Injustice: Gods Among Us as downloadable content. While many fans were excited for the character, some were also upset that the amount of Batman related characters were getting too large. Unfortunately for them, it looks like that trend will continue as NR has confirmed that Batgirl will be the next DLC for Injustice.
It has not yet been revealed how her gadget fighting style will defer from the likes of Batman, but gameplay showing her style off is expected to release in the near future. Considering Lobo releases on May 7th, you can probably expect Batgirl to follow a week or two weeks later.