Robert Meyer Burnett, videographer on Superman Returns and director of the behind-the-scenes documentary Requiem for Krypton: Making 'Superman Returns' wrote briefly, in a BlueTights.net Q&A session, about when the sequel will begin filming:

Angeloz asks if I'm coming back to work on the sequel. The answer is...I'm ALREADY working on the sequel. Bryan, Brandon and the whole merry bunch will be coming back...and filming will probably begin March, 2008, as was always planned from the beginning. The WWII film Bryan plans to shoot over the summer will have NO EFFECT whatsoever on the Superman sequel schedule.
RELATED: Chris Rock Recalls Superman Role That Never Happened: I Was This Close

CLICK HERE to read the story last week about how there had been speculation that Bryan Singer would delay filming the Superman Returns sequel, as he had been tapped to direct an upcoming World War II movie for United Artists.

Dont't forget to also check out: Superman: The Man of Steel