Shinkai Makoto...

... Reveals The Outline of His Next Work

"According to Anime!Anime!, Shinkai Makoto appeared in an Animate concert of his image album "Promise". He revealed draft concept of his new work. He said it will be the longest full scale anime movie he's ever made and the main character is a cheerful girl, who plays an active part of the story. "We have been depicting the process of parting from a beloved person for the last ten years. Now we are trying to take one step ahead of it. If we get separated from our loves, how can we overcome the situation and what awaits after that? We tackle the question through the vivid girl character".

According to Shinkai's web diary, he set to work on the new movie last May mainly with the staff of 5 Centimeters per Second."

Taken from a news report on MAL, translated in context from Anime!Anime! and other sources

I'm excited, Since 5 cm/s was so awesome I'm really looking forward to this.