Honestly, I think Aquaman has a better shot at making the JLA moving than Martian Manhunter! And, heck, Aquaman almost got his own show on the CW a few years back . . . .
Yeah, I think in a world where we've had a Thor movie and are getting an Ant-Man movie and a Guardians of the Galaxy movie, it doesn't make a lot of sense to scoff at the idea of an Aquaman one. That's not to say they'll definitely make one, but it's hardly out of the question.
As I recall, Chris Columbus was developing a Submariner movie a few years, but that seems to have sunk into the Development Abyss.
Universal Pictures had the film rights to Namor for a long time. Columbus was attached to direct at one point and then he left the project and Jonathan Mostow came aboard. From what Kevin Feige has said lately it sounds like Universal's option on the Namor film rights has expired and the rights have reverted to Marvel.
I agree that Gordon-Levitt deserves the chance especially after the build-up at the conclusion of TDKR. Anyone who cares about comic book films will have seen that movie already so minimal exposition is required.
Wasn't the Rock being considered for this role? I think he would have made an excellent Sub-Mariner. Back to the thread at hand, I'd like to submit Rob Kazinsky (TruBlood, Pacific Rim). His performance on this season of TruBlood has him bouncing between dark and cunning to aloof and charming at the drop of a hat. A necessary quality for an actor to possess if he should play Bruce Wayne/Batman. Physically speaking, he's pretty built and six feet tall -- not as tall as Cavill but he wouldn't be peering up at him either. Someone earlier in this thread mentioned Ian Somerhalder. Ever since his bait-and-switch role of "Adam Knight" on Smallville, I've felt he would make a pretty good candidate for Bruce Wayne. Though his casting must come with the condition that he limit the number of times he leers with his eyelids pulled back to their fullest. His eyes are a unique feature for him, but they don't need to pop out of their sockets for us to notice them.
That was the rumor, although nothing was ever officially announced about him being attached to it. He's bound to end up in a DC or Marvel comic book movie eventually. He was attached to star in Lobo and tentatively attached to be in a Shazam movie (either as Captain Marvel or Black Adam - it hadn't been settled which), but those projects got mired in development hell. It wouldn't surprise me if he ended up playing Green Lantern in Justice League.
Unless the producers are dead set on a "year one" Batman (and given this, it sounds like they are proceeding with the idea that Batman has been operating for several years before the team up): Hamm is only three years older than Bale and looks no older. He's approximately six years younger than Downey. If we can have a near-fiftysomething playing Tony Stark there is no reason Hamm can't play Batman.
It would need to be a very different take on Batman for Hamm to be able to use his charm to carry the movie the way RDJ carries Iron Man with his. I'm all for a mature and 'manly' Bruce, but it doesn't seem at all likely. Even Joe Manganiello is probably reaching the upper limit of what the suits are going to want to consider for a 3+ film deal. I don't expect Coster-Waldau to get a call for much the same reasons, though he has the benefit of being on a hit genre show at the moment and looking younger than his years.