Yoda's "there is another" line was just inserted to give the audience the idea that Luke was expendable. He wasn't guaranteed to come out of his rescue attempt alive. But it's obvious in ROTJ that Luke isn't referring to that line because when it was originally said he was in his freaking spaceship and had already lifted off. Sure you could make some wibbly-wobbly handwave and say he heard it through the Force, but it seems much more sensible to say he's referring to Yoda's "another Skywalker" a minute before.