According to the official website, Shinkai Makoto
came back to Japan this month. He had been in London since February 2008 and not been working on anime movie production. Last August, he said he'd like to produce a new anime when he comes back to Tokyo. Presumably, he will set out for a new anime project soon.
He directed the OP movie of "ef - a latter tale" game through the internet during a trip in the middle east Asia before the stay in London.
Source: Shinkai Makoto's diary
According to the official diary on May 31st, Shinkai started working on a new anime. He said he couldn't say anything concrete about the new project.
Picture of his new studio in Shinjuku