It looks like the Gaiking project is still alive, Pacific Rim may not be the only source of mecha action.
Source: Valhalla Entertainment to Produce Gaiking Movie
The live-action Gaiking movie, based on the 1976 anime property, was first announced at Tokyo Anime Fair back in March 2010. Since then the project has remained largely silent. Now word comes along from Gale Anne Hurd's Valhalla Entertainment production company that they are teaming with Toei Animation (original Gaiking animation company) and All Nippon Entertainment Works (ANEW) to develop the Gaiking movie.
The Gaiking movie will feature a young male recruited to be the lead pilot of the Super Robot Gaiking. When an alien menace threatens Earth, only he and his co-pilots can save our planet.
As a reminder, here is the CGI teaser which acted as a sort of proof-of-concept for the film:
The original Gaiking (大空魔竜ガイキング Daikū Maryū Gaiking) also featured a battle with an alien army (Dark Horror Army) and gained some recognition in the West as part of the Shogun Warriors toy line and the anthology Force Five cartoon.
The original Gaiking opening:
Also in 2005, a remake anime aired in Japan titled Gaiking: Legend of Daikyu Maru:
No date has been set yet for the live-action movie.