WWE.com has officially acknowledged Melina's injury, though the details aren't out yet. Some sites have reported a torn ACL. I tend to wait until I hear from WWE.com and Melina herself but it's obvious that she'll be out a while. The WWE is holding an eight Diva tournament to crown a new champion. Storyline points to Maryse, who never got a chance to attempt to regain her title after she, herself, was out with an injury.
With the news that The Hart Dynasty will be heading over to RAW tonight, I personally wouldn't mind seeing Natalya be a surprise winner. Though Maryse is a good solid choice, she's not on the level of Natalya in the ring. Natalya could easily carry the likes of Kelly Kelly and Eve, and put on some solid matches with Gail Kim, which may finally get a reaction out of the crowd for her.
Unfortunately with Melina out, RAW is extremely light in terms of good Diva action. Maryse is entertaining but not a very good wrestler. Kelly Kelly is a crowd favorite but isn't very polished and is far too choreographed. Eve has taken a step back and seen little ring action. The Bellas are basically non-wrestlers at this point and really have no business being championship contenders. Gail gets nothing out of a crowd. Jillian is better as a gimmick, and Alicia needs more growth as a character.
Natalya as champ allows for an opportunity to see more of her on Smackdown as well, and having interaction with the better Divas on that show.
Regardless, Melina's absence will make an impact on the show with no other serious veteran Divas to become crowd favorites.