Before his soul was sealed by the Shinigami he already took half of the kyubi inside him and theorically that half of the fox should be Minatos soul.If we see other Edos like itachi and nagato they were revied in the state they were a little before their deaths so most probably minato is with the other half of kyubi right now and since( in my opinion) he will have a fight with his son he will pass it to him before he vanish just like gaara father.
if that happens naruto will go to a whole new level
No, for the same reason Sarturobi is not merged with the first two Hokages, he did the same thing to them that Minato did to the Kyuubi.
We also clearly see 4 souls leave the Shinigami, the Kyuubi's no where to be seen. Not to mention, even if he was sealed in him, he wasn't sealed in the way we know how Biju are sealed to make Jinchuriki, so he'd likely have no control over the fox.
The action of sealing into ones stomach area doesn't mean that it will go into the user of the jutsu...the user of the jutsu is just animating the Death God...he was the true recipient of the chakra
http://www.mangapanda.com/93-56104-6...apter-504.html - looks like the same seal on Naruto) and not directly into the death god. I am assuming that it is still sealed in him if the seal is still holding...I am also assuming it was not the Kyuubi's soul that got sealed so Minato is not a Jin...But he does have an immense amount of chakra not...
I bet the other half of kyuubi was already reborn into... Sasuke.
and that's the secret how the juubi and madara will be defeated.
Minato is not a jinchuuriki, considering Hashirama and Tobirama aren't in Hiruzen. Hell, even Orochimaru's arms were free and went back to Orochimaru.
I doubt it'll be reborn in Sasuke as well, it'd be bullshit. But considering what Orochimaru's arms did, and possibility with the sealed chakra and Kyuubi's chakra, it could be possible that it looked for the nearest chakra source that could match it best.
If we didn't see it, either Kishi forgot or Yondaime is effectively like Ginkaku and Kinkaku.
Basically a lesser Jinchuuriki without the Kyuubi in his gut
How would that be possible, especially when none of the souls were in Hiruzen?
Maybe it merged with Yondaime, or he sealed it into himself like he was a Jinchuuriki, I dunno.
I did say maybe Kishi forgot
How did either happen though? Would be a major bullshit.
Minato isn't a Jinchuuriki because he doens't have the body necessary to be one until shown otherwise. Also, there's a specific type of seal needed to allow bijuu chakra to mix with the host's own chakra so they can use it. Shiki Fuuin is not that seal.
And the Yin chakra of the Kyuubi won't just gain consciousness and float across the planet to rejoin with Kurama, since once again, it's sealed inside of Minato.