This might seem a little early, but considering the long lead times needed to produce action figures Hasbro's probably already considering these.
Assuming that these would follow along the same lines as the upcoming ANH 25th 2-packs, my ideas would be:
Luke and Vader- during the "I am your father scene."
Chewie and Lando- posed with Chewie choking Lando after Lando has just set them free.
Han and Leia- getting close in the Millenium Falcon
Luke Dagobah with Yoda- Luke seated next to the Jedi Master as he schools him on the Force
Vader and Fett- in the dining hall, Vader holding Han's blaster
Any other ideas? (FYI ESB's 25th is in 2005)