Aquaman was hinted at when Green Arrow, Deathstroke, and Nightwing were. So far two of those four have been confirmed, so either he's on the way or was a red herring. If he is in though, it'll probably be the New 52 Aquaman, which is one of DC's biggest characters right now. He's super serious and likes revenge.
Also, about Lobo and Blue Beetle, they weren't hinted at on Twitter. Swampy, Animal Man, and Batwing were hinted through comic book pictures on twitter like Green Arrow and Nightwing. The Lobo and Blue Beetle thing comes from some website that says they were hinted at in an interview, but they don't have a quote or anything like that.