Read on at your own risk.
The film is dystopian and darker than Empire. Some 30-40 years have passed since Return of the Jedi, and the Empire and New Republic have been locked in a war of attrition. Everyone is languishing and sick of the war. The script, which is described as "too good for JJ Abrams", begins in space, above a desert planet -- presumably Tatooine.
The opening crawl details the ongoing turmoil in the galaxy. How the fall of the Emperor left a void of power, and how the heroes of Endor went into seclusion or kept fighting.
The current state of the war is described as being similar to the European theater of 1944, with the Empire being Germany and the Republic being the Allies. The Republic has finally taken the upper hand.
John Boyega and Daisy Ridley are the male and female leads.
Boyega is a force-sensitive Stormtrooper under command of Gwendoline Christie's character. He defects from the Empire over the course of the movie, ending up stranded on a desert planet (presumed to be Tatooine) during the first act. Having defied orders, Boyega is hunted as a deserter.
TIE fighter wreckage; possibly Boyega's:
https://i.imgur.com/bhTMPuT.jpg
Gwendoline Christie portrays an Inquisitor. The Inquisitors are a group of lightsaber wielding individuals that may or may not be force sensitive and head up the Imperial Remnant. Inquisitors aren't Sith, but they are not Jedi either; they are hounds used to track down force sensitives, and they are implied to have assisted Vader's cleansing.
Christie's Inquisitor:
https://i.imgur.com/JhrbuBy.jpg
Inquisitor's lightsaber:
https://i.imgur.com/cKiSO9B.jpg
Daisy plays Kira, a character living on Tatooine with Max Von Sydow's character. Kira is a dusty survivalist tomboy. Sydow is a broken man from the prequel area that has become mostly cyborg. He is not force sensitive and for some reason collects artifacts that we've seen at critical points during the previous films, particularly ones relating to the Jedi and the Sith. Daisy shares his fascination with history, and she is revealed in Act II to be the daughter of Han and Leia. As someone with force sensitivity, she resents the fact that Luke went into exile before he could train her, and she hopes that the search for force-sensitive artifacts could lead her to him. She keeps her identity as a Solo under wraps in order to keep trouble away.
Sydow's character examining Vader's helmet:
https://i.imgur.com/hjVHT65.jpg; https://i.imgur.com/HAzlSnK.jpg
Sydow's character with Kira:
https://i.imgur.com/pInbshX.jpg
Sydow is a sort of mentor to Kira, and apparently his true identity is an Act III revelation that will surprise a lot of people. The contention is that he is an existing character from the prequel films, and the revelation of his identity will shock viewers.
Sydow's character is "not overtly" a villain, but has some sort of Sith connection.
Sydow's "hideout" is a downed AT-AT. Relics of the war are everywhere in the film; there is a real feeling that the entire galaxy is sick of the deadlock.
AT-AT:
https://i.imgur.com/cm8eBZS.jpg; https://i.imgur.com/FIxykNK.jpg; https://i.imgur.com/LqlrmBZ.jpg
The blue lightsaber in the above picture is apparently the same one Luke lost on Bespin in Empire.
The ball droid from the trailer belongs to Kira.
On the desert planet (again, presumably Tatooine) Boyega meets up with Daisy and Sydow. At the end of the first act, Han Solo and Chewbacca take them all off planet in the Millennium Falcon. Shortly afterward, we learn that "Kira" is Han and Leia's daughter. Again, she keeps her identity secret to avoid unwanted trouble.
Kira's revelation dumbfounds Boyega and "other people."
Chewbacca's life debt extends to Han's whole family, and he is now sporting a robotic arm.
Chewbacca:
https://i.imgur.com/7TGADrf.jpg
Han takes a liking to Boyega. Throughout the film he is in love with Boyega's decision to defy orders and ruin his career in the Imperial military. Han vouches for Boyega, having gone through something similar in his youth.
At some point, Han says the familiar "Hey, it's me!" line. Someone, of course, says the classic "I have a bad feeling about this." These are said to be the only self-referential "smile while rolling your eyes" lines of the film.
When asked whether Han dies, Spoiler Man replied that he will "not spoil the third act." This in and of itself does not reveal anything, but rather comes off as Spoiler Man being audacious, because answering the question is such a way would spoil the third act, if it were true.
Lando's Sullustan co-pilot from Return of the Jedi, Nien Nunb, makes a humorous appearance.
Lando is in the script and has apparently become famous.
Luke Skywalker has secluded himself from the galaxy, training only a handful of students since his exile. He fears for his future; as he comes closer to Yoda levels of power, he becomes more and more secluded. There are no Jedi in the open, but rumors persist that Luke has trained a few since the events of Endor.
Luke first appears in Act II à la Obi Wan dropping his hood in A New Hope. He survives the movie.
Boyega and Daisy become Luke's new apprentices.
Lupita Nyong'o is Luke's current apprentice, and Boyega's eventual love interest.
Luke exiled himself because of the ongoing war. With the galaxy in chaos, he had to ensure his safety so that a new generation could be trained. At least, that's his contention; the fact that he continues to exclude himself despite his great power indicates ulterior motive.
Luke's rumored location:
https://i.imgur.com/N4iJjMm.jpg
Only Han and Leia know where Luke is, a fact we learn aboard a Mon Cal cruiser in the film's second act.
Luke has grown to dislike using his lightsaber, but apparently draws it late in the movie and showcases his abilities against an Inquisitor. It's still green.
Luke speaks to Yoda's force ghost in the film.
Luke has a reveal in the film which, apparently, is stunning.
Leia is the leader of the New Republic. R2D2 and C3PO are with her during the film.
R2D2 and C3PO are the only comic relief characters in the film.
Carrie Fischer's real life daughter, Billie Lourd, plays Leia in a flashback sequence. Darth Vader appears in this flashback as well, which apparently takes place on Endor.
Yavin is in the film, presumably as the Republic's base of operations.
Presumably Yavin:
https://i.imgur.com/dBHibXF.jpg; https://i.imgur.com/blKc7tO.jpg; https://i.imgur.com/tN2vpt3.jpg
The Republic is building a super weapon on a Scandanavian-esque cold and forsaken forest world. Its ultimate purpose is unknown.
The Han Solo archetype is split between Oscar Isaac and Domhnall Gleeson.
Isaac is an ace pilot with the last name "Darklighter" who's been fighting the Imperial forces for years now. He's a bit of a hot shot.
He inherits the Milennium Falcon and is implied to be Kira's eventual love interest.
Domhnall Gleeson plays a scoundrel of sorts.
Adam Driver's character is an ambitious, force-sensitive pilot who falls to the dark side.
He is described as having a transformation that "only begins" in Episode VII.
He builds his own lightsaber (the one we see in the trailer). It's referred to as a "junk" lightsaber, which is why it looks different from that which we are familiar with.
The decision to give his initial lightsaber a cross-guard was apparently made wholly by the art department.
The lightsaber battles are written by Kasdan to be minimalistic and powerful.
Driver wears a mask because half of his face is cyborg.
He goes looking for Andy Serkis' character on the aforementioned Scandanavian-esque forest world, as we see in the teaser.
Driver's character:
https://imageserver.moviepilot.com/...lain-is-darth-revan.jpeg?width=960&height=960
Andy Serkis is some kind of alien Sith exempt from the Rule of Two. He is implied to have existed for a long time, be very powerful, and is the speaker in the teaser.
Serkis is implied to have trained or used Palpatine for some obscure purpose.
Adam Driver receives or builds a new lightsaber after meeting with Serkis.
The Sith are not aligned with the Empire.
Serkis' goals differ from Palpatine's.
Serkis does not play or replace Darth Plagueis.
99.9% of the EU is disregarded.
John Boyega, Daisy Ridley, Oscar Isaac, Domhnall Gleeson, Lupita Nyong'o, Chewbacca, and the droids (presumably Sydow's character and Kira's ball droid) are the new "big 6". Adam Driver and Andy Serkis are Sith and Gwendoline Christie is an Imperial. Characters we still have no knowledge of are those played by Crystal Clarke, Pip Anderson, Christina Chong, Miltos Yerolemou, Greg Grunberg, and Warwick Davis.
Spoiler:
If this film is not good, it's Terminator 3 all over again.
: I speed read everything so I can easily forget it by the time the movie comes out 
