The other hope Yoda speaks of is Luke’s sister Nellith, who has been trained in the Jedi arts at the other side of the galaxy. Leia was just a princess / love interest.
To me that is the thing I would like to have seen the most. I very well love Vader being Luke’s father, but the Luke/Leia thing… it still bugs me.
It was contrived. Totally forced and jarring. And Carrie Fisher´s reaction in the movie was underwhelming (even she admitted this in The Making of Return of the Jedi book). Nellith would have been way better. Fortunately the EU did some interesting things with Jedi Leia.