The following probably doesn't contain spoilers for Star Wars: The Last Jedi. Probably. Still, we might get part of it right, so please be aware of that while reading.
The folks at Lucasfilm and Disney have been fantastically good so far when it comes to protecting details regarding Star Wars: The Last Jedi. We know the name of the movie, but when they announced it we learned none of the rumored titles were accurate. We know the names of many actors who are in the film, but we know none of the characters beyond the ones we've already met. They have yet to release any trailer for the film, so we have no idea what any of the movie will look like or what the story will actually be. Or do we?
Let's face it. When it comes to movies, more often than not, the stories fall into fairly predictable patterns. That doesn't mean they're bad, but if you've seen enough of them you tend to be able to figure out where a movie is going long before you get there. Do we dare try and predict the plot of Star Wars: The Last Jedi. You bet we do.
What follows is one idea for a potential story based on details we know, plot lines set up in _The Force Awaken_s, and decades of experience watching summer movies. Let's see if we can work this out.
Act I: Luke and Rey
One thing we know for certain is that Star Wars: The Last Jedi will pick up immediately following the last scene from Star Wars: The Force Awakens. This means we will open with Rey and Luke Skywalker on a mountaintop and Rey holding out the Jedi's lightsaber. I'm not going to endeavor to guess what the first words spoken are going to be, we're not getting that detailed here. What's important is the basic gist of what happens.
Luke is able to understand a great deal of what has already transpired simply by the fact that Rey is standing there. It's possible that he has even seen some of the events himself thanks to The Force. Rey, for her part, wants answers. She has only the most basic understanding of what The Force is or how she can control it. She needs to understand and Luke is the only one who can teach her. Luke hesitates because the last time he tried to train Jedi things went badly but eventually Rey convinces him to train her. Likely because she convinces him that Kylo Ren is a significant threat after he killed Han Solo. Also, when she tells him about the vision she had, he is sold.
Meanwhile, back at the ranch. The Resistance is plotting their next move. Finn is in recovery from his injuries but he's up and moving around. The destruction of Starkiller Base was a significant blow against The First Order. They are hurt, and they're scattered, but they're far from destroyed. Expect to see some contingent of The First Order, possibly led by Captain Phasma, make a move on the Resistance. The First Order knew what system their base was in, so it would only be a matter of time before they found it. It may take them some time to find the base, which also gives Rey story time to train, but eventually The First Order attacks.
Somewhere while all this is going on, we get our first real reveal moment as we get to set our eyes on the real Supreme Leader Snoke. General Hux and Kylo Ren have traveled to see him as Snoke demanded at the end of The Force Awakens. Snoke said that it was time for Kylo Ren to complete his training. We foresee a combination montage showing both Ren and Rey going through training of some kind. Snoke then lays out to them what the next step in the plan is, kill Luke Skywalker. In the same way that Snoke and Kylo Ren were able to sense Rey's "awakening" in the last film, they can sense her powers growing as she trains, which means they can find her, and with her, Luke.