The animators know absolutely nothing as to what is going to come up in the manga. Kishimoto's family may not even know. It's a very secretive art. Did you know how pysched people were for Shippuuden, I think Gaiden would've slowed that down. They put that bit with Sasuke as an appeaser, they'll get to Gaiden at some other time, probably after a major arc is my guess.