While I'll likely buy whatever this turns out to be, I'd prefer it if Miyazaki just got to work on the next film instead...
Miyazaki has been moving in and out of retirement, and its a miracle he's worked on ay movies at all, with rumors of his physical conditions and state he feels the ANime industry is in. But even now there's rumors he's starting work on another movie, aside from Ponyo, so its not like Ni no Kuni is distracting from any new movie. Not anymore than his work on the Ghibli Museum, co-producing other Ghibli works and overseeing the major productions of Ghibli itself.
Wait, what?! I'm so confuzzled.
Tales from Earthsea was a movie done by Miyazaki's son, Miyazaki Goro. And considered by many not to be up to the quality of the works of his dad. Or even the other works produced under Ghibli by other directors such as Whisper of the Heart (Yoshifumi Kondo), Grave of the Fireflies (Isao Takahata) or Ocean Waves (Tomomi Mochizuki). Miyazaki himself even commented he didn't want his son to make the movie because he felt 'he wasn't ready to direct a movie yet'. But it was made...and its your opinion to its quality.