Carthage said:
During the part where Luke is blasting off in his ship to Bespin, Obi wan is talking to Yoda and says "He's our only hope", Yoda says "No there is another". What exactly did he mean by that? Was he referring to Luke's course of action and how it would change, or that there was another way to do things?
The lines were as follows:
YODA
(sighs) Told you, I did. Reckless is he. Now matters are worse.
BEN
That boy is our last hope.
YODA
(looks up) No. There is another.
The context of this conversation is just after Luke rushed off to help his friends against their advice to stay and finish his training.
Remember Yoda was against his training but Obi-wan insisted. In Obi-wan's eyes Luke was their only hope in defeating the Emperor and Vader. Not knowing Yoda's secret about there being another Skywalker. Which he presumably reveals to Obi-wan offscreen following this scene.
During the writing of ESB, George had originally planned for a nine episode saga that could be stretched out to twelve if the box office was good enough.
Episode VII was originally going to be about Luke going off into the galaxy to find his long lost sister. But, after the stress of the ESB production Lucas decided to just cap the series off after just three. Which is why they shoehorned in the whole Leia is his sister stuff at the last minute.