One could say the title says it all. Undoubtedly, as many may have noticed Luke Skywalker, played by Mark Hamil, is The Last of the Jedi who will be the focal point of the movie alongside Rey (Daisy Ridley). However, what does this mean with respects to the Force and those who wield it?
What we have primarily seen in the majority of Star Wars canon suggests that the inhabitants of the galaxy are subject to a constant power struggle between the light and the dark side of the Force, and between users that are either Jedi or Sith. Throughout the original series we see what remains of the Jedi Order consisting of light side users Obi-Wan Kenobi and Master Yoda along with a padawan in training turned Jedi Knight in Luke Skywalker. In contrast, the dark side of the Force is wielded by the Sith, who utilize the rule of two, featuring a Sith Lord afraid of losing his power, and his apprentice always looking to overthrow his Master. This theme of Jedi vs Sith is constant even in the prequels and going back to The Old Republic. However, it isn't until the more recent series of Star Wars movies and the current timeline that we may be witnessing a change in this framework.
Star Wars: The Last Jedi will pick up right where Star Wars: The Force Awakens left off with Rey finding Luke Skywalker and seeking training in the ways of the Force, and it's here that we may see the beginning of the end of the Jedi. We may already have seen the end of the Sith and not have realized it within The Force Awakens.
If you remember, during that movie Rey receives a Force vision, and additionally we get a explanation of sorts of the events that have taken place after Return of the Jedi. With the Sith defeated, Luke attempts to train a new group of young Jedi, along with the dark side user Kylo Ren. However, Ren betrays Luke, is seduced by Supreme Leader Snoke, and forms the Knights of Ren. It's possible parts of the betrayal are what Rey sees in her vision. But, important to note is that Kylo Ren is the only lightsaber wielder in this vision that also depicts the Knights of Ren. This type of grouping is not something we have seen from Star Wars canon in the past; sure the Sith will form alliances to their benefit but they have no equals and for the most part strictly adhere to the rule of two. Exceptions are likely made to this when an apprentice is seeking to usurp their Master by recruiting an apprentice of his own, or if a Master is looking to replace an apprentice, he will seek an additional one to defeat the current. Also important to note is that while Supreme Leader Snoke is versed in the ways of the Sith, he is not one! J.J. Abrams confirmed this himself. It's possible he may prefer to borrow certain aspects of the Sith, but seek a different means of gaining power. There is also the possibility that the Knights of Ren are darkside users along with Kylo Ren, but to a lesser degree. This can be assumed due to what we have seen from Rogue One: A Star Wars story.
During Rogue One we get to know the band of Rebels know as the Order of the Whills, and one of its members Chirrut Imwhe. Chirrut is not a Jedi, but is Force sensitive and exceptional in a way that is comparable to a Jedi. This is something that we have not seen previously in Star Wars canon and it stands to reason that there may be others like him. By the end of the film we even see his companion Buaze Malbus able to avoid blaster fire much like a force wielder would be capable of. Could the Knights of Ren be a force sensitive group drawing similarities to the Order of the Whills? It doesn't end there though, Star Wars: Rebels has also offered hints to changes in the way we may perceive the Force.
The addition of the character of the Bendu, one who exists in between the light and dark sides of the Force, seems to add more depth to the thought of simply good vs. evil. Additionally, current Jedi Knight Kanan Jarrus, alluded to anyone being capable of using the Force. While training Sabine Wren, a Mandalorian non Force user, to wield the dark saber he mentioned that the Force is within every living being, though obviously some are more sensitive than others. Ezra Bridger is also something of an anomaly when it comes to Star Wars lore. At one point he seemingly was able to use both sides of the Force. While working with Darth Maul he was able to unlock a Sith holocron. Lastly, he isn't completely acceptable of to Kanan's training in the ways of the Jedi.
All that said, it brings us full circle back to Rey and her training with Luke Skywalker. Could she be training, not to be a Jedi, but something else entirely, capable of using both sides of the Force? It lends itself to the thought that it isn't the light side or the dark side of the Force that determines a users actions. Whether light or dark side user, perhaps the power can be used for good or evil. However, I don't feel this spells doom and gloom necessarily for Luke or Rebel characters such as Ezra and Sabine. That said, this may be a death note for someone like Kanan, who survived Order 66, unless of course he lets go of the ways of the Jedi much like Ahsoka Tano, former padawan to Anakin Skywalker and white light saber wielder, who revealed on Rebels that she is "no Jedi!" So I do believe this series will be the end of the Jedi, but that doesn't have to be a bad thing. Rey could turn out to be the one who brings balance to the Force by truly controlling all aspects of it, a theme that ran through Star Wars episodes 1-3. She could open the Galaxy to training and knowledge in the Force even if they don't have great sensitivity towards the Force. Lastly, perhaps she is "The Other" Yoda spoke of in the original trilogy who could save us all.