Things took quite an unexpected turn when the poster and the trailer for The Last Jedi were released at this year's Star Wars Celebration: it sort of seems like Luke might be on the Dark Side in The Last Jedi. Maybe. Kinda. Sorta. It could all just be misdirection and fans could just be jumping to some rather hasty conclusions, but the Luke we meet in the first ever produced footage of the film does not show our favorite Jedi in the best light.
Secondly, the poster has him alongside Kylo Ren, both bathed in blood red light. Rey seems to be positioned as the savior in the middle, while Kylo and Luke appears to be halves of the same whole. Add to that, the fact that in the trailer, Luke very clearly says he wants the Jedi to end. This is a darker, more negative Luke than we've ever encountered.
What's more, is what Daisy Ridley said about Luke & Rey meeting, namely that we should temper our expectations.
"It’s difficult when you meet your heroes because it might not be what you expect," she said. Of course, it also appears that Luke is training Rey, which complicates the matter. Why would he train her, if only to end the Jedi?
The idea, however half-cocked, that Luke could possible no longer be totally on the Light Side is actually kind of delicious. It would certainly change up the narrative that we're all expecting: the practical buddy comedy fantasy between Rey and Luke that we've all got written in our heads. Plus, if the most common Rey parentage theory turns out to be true (Luke as her father), it would be far more satisfying if that relationship was less of a happy reunion and more about making good with the fact that Rey's hero and father is actually no longer the great man she thought he was. Rey's fantasy of finally meeting her family would be much like Luke's eventual meeting with his father, after years of wondering: Devastating and full of fraught emotion.
The Last Jedi is in the Empire Strikes Back position in this new trilogy, and the twist of Luke being on the Dark Side (if he is Rey's father) would be a wonderful way to pay homage to the trajectory of the original trilogy, while sending Luke into his father's footsteps, and allowing history to keep repeating itself as well, history tends to do.
Look, I like Luke on my side as much as the next fan, but just think about how dark and wonderful that could be. Bring on the Dark Side, Lucasfilm. Bring. it. on.