According to this site, Edgar Wright's Ant-Man will begin shooting in January 2013 for the late 2015 release. Nathan Fillion (pretty much every main guy in any Whedon project) was mentioned for the lead role in Hank Pym, the original Ant-Man.
Personally, the more time they have to work on it, the better. The script's been in the works since the first Iron Man came out way back in 2008, so we know this movie won't be half-assed. Fillion appears to be the fan favorite for the role, but in all honesty, he wouldn't be my first choice (even though I know he'd be ok for the role). I would take that bit of news with a grain of salt, as Fillion seems reluctant to take on the role (and Star-Lord's for that matter) in recent interviews. Either way, I think he'd play the part well.