Orochimaru did not return, nor will he ever return. Kabuto has surpassed him to such a degree that Orochimaru's return would be meaningless. Oro is my favorite char, but I am not a fanboy without reasoning.
Itachi is merely injured, and Kabuto is trying to add a new tag inside his head to take him back as his summon. He won't be able to defend himself during the healing process so he'll need Sasuke to save him again.
Those representations of the Sound Five and Orochimaru are not summons. They are mere DNA that Kabuto assimilated into himself and he's giving them visual form with Sakon's body altering technique. Kabuto could form Karin's face on his crotch if he wanted to, despite how she's alive right now.
There is not a single shred of evidence that the Eternal Mangekyo Sharingan gives you any new abilities. Even the forbidden techniques are accessible with the Mangekyo Sharingan. The EMS just allows you to keep spamming MS techniques without losing your light. At the very best the EMS would give you any of the unique ocular powers from the person you fused your eyes with. Say perhaps Itachi's Totsuka or Yata Mirror, but not even that has been shown yet.
