I figure that the next time Sasuke goes to Naruto's inner world to squash the 9-Tails, he is going to be in a for a surprise: either outright rejection, or some piece of Itachi waiting for him.

Thing is Sasuke was shown to be able to disperse the 9-Tails at will a while back. This is part of having a Sharingan and Itachi would know it. What better weapon to give Naruto than one that would allow him to confront Sasuke with the power of the 9-Tails?

My guess is both: Itachi will speak to Sasuke, much like the 4th did Naruto, with the 9-Tails and Naruto in audience. Sasuke will go all emo and pursue the path of failure. Itachi will kick him out the door and Naruto will kick his ass in the real world.