Cinematical is reporting that Bradley Cooper (from The A-Team, but I know him best from Alias) is the rumored frontrunner to play The Flash. Interestingly, the story also mentions that Ryan Reynolds was set to play The Flash about five years ago but that project fell through (plus he is now Green Lantern). In the comments section of this story, quite a few people have voiced the opinion that Reynolds would make a better Flash and Cooper a better Green Lantern. Personally I think that Reynolds is beyond perfect to play Green Lantern Hal Jordan and I think that Cooper could pull off The Flash, but I guess the big question is, which Flash would he play? I suspect that DC and Warner Brothers would elect to go with the Barry Allen Flash over the Wally West Flash (especially since Barry is now back, alive and running in the DC Universe).
My biggest hope for this project is that they bring in DC writer Geoff Johns to help with the script or at least contact him for advice in the writing process. He has proven to be one of the best writers in comics today and knows the character of The Flash (see The Flash: Rebirth).