Kylo Ren is a very changed man.
He doesn't utter a single word, and we only see one actual shot of him in the trailer, but it is very obvious that Kylo Ren is not the same man we saw at the end of Star Wars: The Force Awakens. Killing your own father clearly changes a person. Before we actually see Kylo Ren, aka Ben Solo, in the trailer, we see a very fascinating and ominous image of his helmet totally and completely smashed. Did he have another one of his emo fits of rage and his helmet was a casualty of said rage? Did someone smash it without his permission? Was it a very intentional smashing? There is no context for it, but when we finally do see Kylo Ren, he is without his helmet. So he didn't seem to be in a rush to find a replacement. When we do actually see him, he is unmistakably in a dark place. He has his lightsaber up and a dark yet hollow look in his eyes. But what is really telling is the scar that he has on his face, which looks to be a result of his lightsaber battle with Rey in Star Wars: The Force Awakens. Even without a single word coming from his mouth, this trailer presents us with a seemingly darker and conflicted Kylo ren.
Old Jedi teachings will play an important role.
One of the most fascinating sequences in the first trailer for Star Wars: The Last Jedi came in the form of what looked to be some old books containing Jedi teachings, with an unknown figure having a look at them. The Jedi symbol can be seen on one of the dusty books, with an unidentified, gloved hand brushing some of the dust away. It seems very much like these books contain some ancient Jedi teachings. As to who owns these books and what books they might be exactly? That could be the million dollar question from the trailer. For those who have kept up with the Star Wars comic, we know that Luke discovered old journals from Obi-Wan Kenobi at one point. So maybe Luke has been hiding these somewhere? That is just speculative, but these books definitely seem to contain some ancient Jedi knowledge.
Yoda and Obi-Wan Kenobi are looming near Rey.
Just before the sequence that reveals what appear to be books containing ancient Jedi Knowledge and/or teachings, there is something a bit quiet that is seriously exciting. As the camera zooms in on the books, there is some very quiet voice over that sounds like none other than the Jedi Master himself, Yoda. It is only three syllables that are very difficult to make out, because the score is playing quite loudly over it, but it sounds very much like Frank Oz doing the voice of Yoda. There have been rumors that Yoda will appear as a Force ghost in Star Wars: The Last Jedi for a very long time and, during SXSW, Frank Oz even alluded to his potential involvement with the movie. Since these books seem to contain Jedi teachings and Luke is going to be training Rey, it makes every bit of sense that Yoda would be showing up in some way or another. This seems to be our very first hint of that and that should be more than enough to get Star Wars fans pumped even more about this movie.