DeeDee Flores of Samy’s Camera has written in to inform us that:

“The Panasonic GH-4 camera fits inside the Nauticam GH-3 housing with full functionality.”

This is great news for LUMIX DMC GH-3 owners looking to upgrade to the 4K performance of the DMC GH-4. It is likely, although not definite, that other GH-3 housings will work with the GH-4 too.