Robin Williams is in negotiations to reprise his role as Teddy Roosevelt in Night at the Museum 3. He played the American president in 2006's Night at the Museum and the 2009 sequel Night at the Museum: Battle of the Smithsonian.
Ben Stiller is also returning to star as museum security guard Larry Daley. We reported in September that production is beginning in February 2014 in London and Vancouver. The sequel is set in London as well, which may take advantage of the Natural History Museum or other historical facilities, although no story details have been confirmed.
Shawn Levy is directing, although it still isn't known who is providing the screenplay. Thomas Lennon and Robert Ben Garant wrote the first two movies and, while they hinted that they were writing the sequel back in 2010, neither writer has been confirmed as of yet.