So, as we all know by now: Miyamoto is busy with a new IP...we don´t know anything else !

a busy bee Mario for illustration purpose

But that shouldn´t stop us from getting hyped beyond believe and setting our expactations incredibly high so that nothing he can come up with can ever satisfy us (read: The Internet way )

But which Studio do you think is currently developing the title ?

My pick would go to Hal LAb or EAD Tokyo 1.

Hal hasn´t done anything lately (since Face Raider´s for the 3DS in 2011, and Kirby´s Dream Collection in 2012) and they are a huge Studio (145 emplyees by Wiki)

EAD Tokyo 1´s last big game was Super Mario Galaxy in 2007, I know that Studio 1 and 2 shuffle their developers around when one project demands more workforce than the other, but their last project was co-developing Zelda OoT 3D...in 2011.

What do you think ?

EAD Tokyo 1 is working on a project, but it's not Miyamoto's. They are working on Yoshiaki Koizumi's game, which he said we'll be finding out about soon. I would say Miyamoto's project is being done in Kyoto at EAD. Probably by a new team in group 2 or 5. But for all we know the groups may have all been changed. They have been hiring lots of new staff. A new headquarters which is almost done. There's been lots of talk of reorganization of staff there.

Probably wichever team just made Pikmin 3 and is now available.

It is going to be one of the main internal groups, if Miyamoto is as involved as many speculate, he is working on the project while sticking close to the home office.

chillingo perhaps?

It'll most likely be an EAD Group. Miyamoto seems to work a lot closer with them on his newer projects than he does with other Nintendo studios. Also, I doubt HAL will be working on a new IP since they are most likely working on Kirby and (I think) they still work on Super Smash Bros.

Double Helix.

a good point, it really does make more sense that it will be one of the internal EADs if he is so closely involved...but which one ? 4 has made Pikmin3 NSMBU and 2 in such a short time...the Zelda Team is busy with 3 project at the same time....EAD 5 ?

(It still boggles the mind that this shoddy developer gets to stain so many beloved franchises....Silent Hill, Killer Instinct, Strider....what next Half Life 3 by DH ???)