"Pacific Rim," a treatment/spec-script from Travis Beacham, has the good fortune of being Guillermo del Toro's next movie... and the bad fortune of being the movie del Toro "fell back" on when "At The Mountains of Madness" fell apart a few months ago - meaning that everyone was too upset about "Mountains" to give it the proper "Holy shit del Toro doing a giant monster movie!!!" hyping it deserved. Now that it's begun to add a cast, maybe that can turn around.
"Rim" has been more-or-less pitched as "Gundam vs. Godzilla" - or, more appropriately, "Stuff From Japanese Pop-Culture Americans Like: The Movie." It's premise involves an interdimensional portal opening up in the Pacific Ocean that starts spitting out angry giant-scale monsters. The good guys are humans who pilot "building-sized" robots to fight them. That'll work.
Elba and "Sons of Anarchy's" Charlie Hunnam are signed to play the two human leads. There's been some speculation that the script may have been reworked so as to not focus too much of the monster-destruction business on Japan (which it initially did) in the wake of the recent disasters there.