What do we know about Goro's Miyazaki's next film?

Okay, after his fantastic drama, From Up on Poppy Hill, it has been rumoured the Goro Miyazaki will be working on a samurai film. So basically I want to see how much we information we collectively know about it.
It's said in this article that "...Goro Miyazaki is planning a samurai period work that combines fact and fiction. Suzuki told filmmaker Shunji Iwai that Goro Miyazaki's project is set in the northeastern Tohoku region of Japan during the Middle Ages."

It could posssibly a) be loosely based on historical tales or b) based on his father's manga or c) or both. Miyazaki the younger mentioned back in 2011 that 'I think it'll be about two years from now. Actually, my dad has begun making it now. It's amazing."
On IMDB it says he has a project called Hôjôkishiki in development, based on the book by Yoshie Hotta.
This blog post may be helpful but it was posted way back in 2008, before Poppy Hill's completion: http://jfilmpowwow.blogspot.co.uk/2008/09/studio-ghibli-to-take-on-works-of.html
Basically I'm just really interested in what this dude's got up next. Both him and Yonebayashi appear to be the two lead directors of the next generation of Ghibli. So, does anyone know anything else about what Miyazaki the younger is doing?