I'd say Sasuke, as not only does Kabuto want his Sharingan, but they both have scores to settle with each other.
Kabuto is now using Itachi like a puppet. Since Sasuke and Kabuto are likely to meet, I'm sure that he'll summon Itachi to "psychologically" twist with Sasuke. The only problem with that, is that with most victims, it plays on their emotions, which makes them weaker, or handicapped. Sasuke only gets stronger as his anger grows.
It actually makes sense that Kabuto would summon Itachi to fight alongside him for Sasuke, as Itachi isn't doing anything but chilling somewhere at the moment.