I think Rey and Luke’s story in The Last Jedi is going to be structured like a love story. Love stories are ultimately about two people coming to love each other and learning how to have a relationship with each other and that’s exactly what Rey and Luke’s story is only the love is familial rather than romantic.
The love stories that we’ve seen in SW both begin with one character having a crush (Anakin on Padme and Han on Leia) where they love the other person even though they aren’t yet part of a romantic relationship. Replace that in The Last Jedi with Luke’s unconditional love for his daughter even though he and Rey are effectively complete strangers. In both Attack of the Clones and the Empire Strikes Back what prevents the characters from being happy couples is emotional baggage that causes friction and conflict in their relationship: Anakin and Padme’s sense of duty and feeling that it would be wrong for them to be together and Han and Leia being too proud to be emotionally vulnerable by admitting they love each other. For Luke and Rey the emotional baggage is Luke’s guilt and Rey’s abandonment issues and her disappointment in him.
Attack of the Clones and the Empire Strikes Back intersperse the scenes with dramatic conflict with romantic scenes. The Last Jedi will likely intersperse dramatic scenes with very tender father daughter scenes. The love stories in both cases build up to a love pledge: when Anakin and Padme enter the arena and “I love you” “I know”. The Last Jedi will likely build up to a love pledge of sorts: either the first time Rey calls Luke “Father” or the first time she tells him she loves him. Something then happens either at the end of the film or between the second and third film that forces the characters apart: Han is frozen in carbonite and the Clone Wars start taking Anakin away from Padme for long periods of time. The Last Jedi will likely end with external forces forcing Luke and Rey apart. Revenge of the Sith and Return of the Jedi then both feature an emotional reunion: Padme telling Anakin she’s pregnant and Leia unfreezing Han. IX will likely feature and emotional reunion between Luke and Rey (though I think it will be much later in the movie).
note: none of this precludes a romance between Finn and Rose but as Rian Johnson said the “beating heart” of The Last Jedi is the relationship between Rey and Luke.