The making of Empire book alludes to the fact that Lucas was trying to deal with both the possibility of Harrison not coming back for another film, (so Han gets frozen and taken away to Jabba) and the possible mortality of his other star, hence the "no, there is another" line as a way out.

Remember, Mark Hamill had a near fatal car crash between SW and Empire. One alleged reason the Wampa bloodies Luke up is to explain away why he might look different after the real life injuries Hamill endured.

I don't believe the "other" was intended to be Leia at the time though, in spite of the fact she sensed Luke's cry for help. Because if Lucas really had that in mind, it makes that kiss earlier in the film really really icky! ;)