According to Rotten Tomatoes, Bryan Singer is lined up to direct The Mayor of Castro Street after he finishes his current film, Valkyrie:

"Bryan Singer had previously told us that the Superman Returns sequel Superman: The Man of Steel would be his next film after Valkyrie. His producers tell another story. Neil Meron and Craig Zadan have Singer lined up to direct The Mayor of Castro Street, a story of gay rights activist Harvey Milk, within a year.
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"The next Superman, that's a ways off," claimed Meron, with Zadan adding. "Don't worry about it. Trust me. We may even start preproduction on Harvey Milk while he's on post production on the Tom Cruise movie."

Rotten Tomatoes goes on to say that Chris McQuarrie will write the screenplay to The Mayor of Castro Street which Bryan Singer will be looking to direct. The film has been in the works for 15 years and originally had Oliver Stone and Robin Williams attached to the project.

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