My predictions for The Force Awakens proved reasonably popular, and not wholly inaccurate, so I’d like to try my hand at the second film in this new trilogy.

There are two ways of preemptively thinking about The Last Jedi:

1) It is going to be the same story beats as The Empire Strikes Back.

2) Everything has been misdirection so far, and while it does repeat “set pieces” from Star Wars V, it will turn events on their heads.

Basically, it will be similar to The Empire Strikes Back. Which is a crushing reality I am trying to prepare myself for before its release.
Don’t believe me? Look at the trailer again: An old Jedi master training the protagonist (after the old “master” died in the previous film); an objectively “white” planet (Hoth) with quadruped First Order walkers (AT-ATs) battling with rebel hover vehicles (Snow Speeders); the lead antagonist extending his hand towards the protagonist (Vader and Luke on Bespin); Rey speaks of “a cave”, much like Luke’s vision on Dahgobah. The only changes in pattern are the inclusions of Snoke and Leia.
(And I say all of this as someone who liked The Force Awakens, but that’s because TFA had a lot of work to do. It was damage control).

So what can we deduce? Disney know they are on a good thing. In fact Disney has praised director Rian Johnson for his work on The Last Jedi and has given him the go-ahead for an entire new trilogy.
Whatever happens, Disney is happy.

Rey is not going to join The Darkside.
She just isn’t. It would be cool, and it would be a reason for Luke to freak out like he does in the trailer. But Disney will not be making their leading girl a villain. As eluded to with the first poster’s design, I believe Rey will learn both Light and Dark Sides and use them both, to understand you cannot have one without the other. Didn’t Return of the Jedi‘s exuberant “Yeah, we defeated one half of The Force!” feel extreme in some ways?
“The Last Jedi”, indeed. Snoke and Kylo have never been referred to as Sith, in fact, Kylo Ren is basically play-acting as a Sith because he worships everything his grandfather was “Let the past die, kill it.” says Kylo in the trailer. So the Sith are dead and this is the end of the Jedi. Luke is the last Jedi.
So if Rey is not a Jedi, and she isn’t (as decreed by shadowy PR people, and me) becoming a villain, she will become something new.

Kylo Ren cannot be redeemed.
Spoilers: he killed Han Solo. That’s… no. To fully redeem Kylo would be absurd. He is probably going to aid Rey in becoming familiar with the Dark Side (which will probably end with the awful collision between her and Snoke, as seen in the trailer) but he will be ignorant of her intentions for doing so. He will probably believe she is joining them, that he has won and done what Snoke asked of him. This could be written in such a way that the audience believes she has joined them, momentarily.
Maybe, maybe, in Star Wars IX, Kylo can redeem himself (ala Vader in Return of the Jedi).

Han Solo is not coming back.
Don’t be stupid. Harrison Ford has washed his hands of the franchise, why else was he so good in The Force Awakens? He’s dead. No Force Ghost or anything. Deal with it.

Leia won’t die.
To kill the late and iconic Carrie Fisher would be a massively risky move for Disney. I highly doubt they would commit to it. There is pulling heartstrings and then there’s destroying several generations and a cultural icon. Kylo will probably stay his hand, or be forced to retreat before he can kill her, again, this is misdirection from the trailer. Perhaps Leia will be used as a means to personify Kylo’s lingering doubt and the Light lingering inside of him.

Luke won’t die.
Mark Hamill is a bankable name in the Star Wars franchise. With Ford out and Leia’s part in Star Wars IX sadly drastically reduced, Luke will probably have a further part to play. Could he be a Force Ghost in Star Wars IX instead?

Poe/Finn.
Could this be a thing? Disney has been adding diversity into their films very subtly recently, and what with Rey being fully involved with the plot I doubt she can have time to fall in love with one of them. Plus, Poe Damaron was originally meant to die in The Force Awakens, so you can imagine his character is something of a wild card in the greater design of the franchise (Wedge Antilles was something of an anomaly in the original trilogy, a fun, welcome anomaly; he survives all three films but is very much in the background). There has been a lot of chatter since TFA released about Poe and Finn getting together. Could the two men have a relationship, filling the last checklist requirement of copying Empire Strikes Back, Leia and Han’s relationship? It would certainly add tension in the battles that Poe and Finn find themselves in.

Kylo and Rey aren’t related.
Contrary to popular belief and my theories thus far, I don’t think the two characters are related. While this would round out the parallels with Empire Strikes Back‘s “I am your father” moment, it would be cheesy to do it again, no matter how subtly it is played.
If they are related and I am wrong… well, The Last Jedi will lose marks in my eyes.

Some of these turned into personal preferences rather than actual predictions, but these are my thoughts as to how The Last Jedi will play out. Roughly.