Can you point me to where they said this? I didn't hear that, I just heard them say he's playing Victor Von Doom. I never heard them discuss variants at all.
Jeff Sneider is reporting that he got an email from a source on May 12 confirming that RDJ would be back, and that he'd be a Tony Stark from another universe who became Dr. Doom. He also says that this Doom will have a cameo at the end of F4.