I'm taking this rumor with a huge block of salt. Yesterday an article popped up (from a Bulgarian source mind you) suggesting that Meryl will be shooting an action movie with Cameron Diaz near Sofia. The article compared the project to The Expendables, and is evidently being produced by action film producer Avi Lerner.
This type of movie seems very unlike most projects Meryl typically does. She's been on record saying that she thinks it's important for actors to be aware of what they're "putting out there," in regard to violent films. I certainly enjoy when Meryl does a variety of roles, but this just seems too out there. As usual, time will tell if we end up getting any additional information suggesting this project is legit. I wouldn't hold my breath.