korell: ...therefore the kiss was part of the trilogy.
AndyBuzz: And what makes you think that he didn't make things up as he went along? I was reading a thread in imdb (hey, I know but we talkin' about Star Wars here... whadayawant? Encyclopedia Britannica?), that in the rough draft the "there is another" would refer to a lost twin brother of Luke that would be the main character in the next trilogy. But personal issues and a change in focus made Lucas wrap things up much faster and the bro became a sis. Have no clue if it has any merit, but here ya go.
The very nature of creative work is to make things up. When he did it we can never know, but most likely the main plotlines were done beforehand and other details done as and when to flesh it out somewhat.
As for the kiss, you were making it seem as though it was done in the first film and so nothing to do with the trilogy.
AndyBuzz: I have a strong feeling that initially he didn't even plan for a trilogy, what with the implied spark between princess Leia and Luke and a scene with them kissing.
So that is why I pointed out that it happened in the second film (just after Luke got released from the bacta tank, recovering from his time out in the cold harsh snow and ice of Hoth) meaning that it must have been part of the trilogy.