Easterhay said: That said, if he hadn't decided on Leia being "the other" in ESB, how do we explain her use of The Force towards the end of the film where she suddenly sense Luke is still alive and they should go back to him?

Luke specifically attempted to contact Leia with the Force. She did not suddenly sense Luke: he called to her, after first trying Ben. That is why she knew. To whom else could he call out for rescue with the Force? Han was in carbonite, Lando's allegiance was suspect at best and Luke did not really know him, presumably the droids could not be spoken to with the Force as they were not living beings, and growling Chewie was hardly the best choice to pass on any message. Chewie! Hear me, Chewie! just doesn't work.

Lucas had no choice but to have Luke contact Leia as a deus ex machina, as she was the only one on the Falcon whom he could plausibly contact. (There is also the fact that the love triangle had yet to be resolved, so the scene could also have served as a sign of Luke's connection with Leia, if Lucas had decided to resolve the triangle the other way.) I think a significance can be read into this scene -- with Leia as "the other" -- just as a significance could be read into Ben's pause after Luke's question in ANH, but it was not written with that in mind originally.