Knights of Ren missing from TLJ as they were on mission to find a device belonging to Vader called the "wayfinder", or simply an object that points the way to Palpatine's unknown regions hideout. Palps has one, Vader had one. This is the object Rey touches which causes her to see the dark vision of herself.
Palps wants Rey turned bad as she is his granddaughter. Parents did not abandon her, they were murdered for hiding her. The ship in the vision belongs to the person tasked to hide her on Jakku.
Gallius Rax was discovered by Palpatine on Jakku years before the first and second death stars. Palpatine tasks him with setting the "failsafe plan" in motion in the unknown regions. Each new star destroyer in that fleet is equipped with death star technology and has the ability to obliterate a planet.

Leia sends the Resistance mod squad to find an "old contact" who might be able to help them find their way to the unknown regions lair of Sidious. This contact has more experience with the unknown regions than any other person Leia knows. The group go to the planet we see with what looks like a state fair going on and try to blend in. Chewbacca of course stands out like sore thumb and the contact recognizes him immediately and reveals himself to the group. This is Lando.
Lando was married and had a child that was stolen from him by the first order. This child managed to escape and has been hiding on Endor. This is one of the new characters that will be introduced in the film. Pretty convenient, huh? So, happy endings for Lando and his baby girl.

They can now actually fight across space-time and injure each other. Derp!

When we first see Sidious in this movie, he will look older and more decrepit than petrified dinosaur shit. He will confirm to Kylo that he did indeed survive his betrayal at Endor and is not a clone.
Toward the end of the movie he will use some sort of force power to drain Kylo and/or Rey of their life force and rejuvenate himself to a new state where he will look and move like he did in ROTS post-Windu fight. At that time, his clothing will look like what he wore during the Clone Wars when he fought Maul and Savage Oppress. Kylo will be dead by Palpatine's hand at this point in the movie, and Mary Sue will of course defeat him. How? She will be joined by the force ghosts of Luke and Leia( no, I am not fucking kidding )who will help her end old Palpy once and for all.

So Mary Sue and the mod squad go to a planet called "Exodal" in search of a contact that Leia tells them may be able to help them find the way to the lair of Sidious in the unknown regions. Lando recognizes Chewie and introduces himself to the crew in private. Lando and Luke had been here years before searching for a Sith dagger in the possession of a character named "Ochi". They tracked him to Exodal and then lost the scent at that point. Lando stayed on Exodal because his daughter had been stolen from him by the first order, and he felt that his best chance of finding her would be to stay on planet and wait for Ochi to resurface as he was responsible for not only Lando's child, but other children across the galaxy that he had sold to the first order or had been sent to specifically to capture.
Lando takes the mod squad to the last known coordinates for Ochi and bids them farewell. Rey can sense a signal in the force and they begin moving toward it. The ground gives way and they end up in a series of underground tunnels and caverns. They find the remains of Ochi along with his ship. Rey recognizes the ship as the one flying away from Jakku in her flashback to childhood. Ochi had killed her parents with the dagger on Jakku but he was never able to find Rey because they had hid her so well. Rey's parents were NOT scavengers or junkers, at least one of them was a force-sensitive from the Palpatine bloodline. Yes, Sidious had fathered children or at least one child during his lifetime. The Dagger is in the possession of Kylo Ren.
They take the ship and escape from Exodal because the first order had shown up( Kylo using his mind-meld to find their location )and had already taken the Falcon and Chewie prisoner. Somehow they get the dagger from Kylo after boarding his Star Destroyer using a device which allows them to pass com-scans, appearing as a "friendly" vessel. C3P-0 can't translate the writing on the dagger due to a restriction in his programming forbidding him to share translations of Sith writing, so he voluntarily undergoes a memory wipe to remove the restriction.( it is reported that the way this scene is done creates the most emotional scene in the movie ) He translates the dagger writing which includes coordinates to the lair of Sidious in the unknown regions, and Rey takes off to go confront Sidious. ( 3P-O's red eyes are a result of the memory wipe, and Rey's backflip over the tie interceptor is her stalling Kylo Ren so the others can escape )
When they arrive on Endor, they discover a young woman who had escaped from the first order as a child and has been living and hiding on Endor since her escape. This is Lando's lost daughter( isn't that special AND convenient?! ).

The movie opens with Luke training Leia as a Jedi. She tells Luke that she is pregnant with Ben Solo, and that she must put her training on hold. She gives Luke her lightsaber to hold for safekeeping.

I've heard NOTHING about Rose in this movie so far. Maybe we got lucky and won't have to endure her at all.

At one point we will see Hux and the new General( Pryde/Pride? )rounding up children at the behest of Sidious to crew and staff his armada of Star Destroyers. There is no conflict between Sidious and the First Order, Kylo accepts his authority and vision after spending some time with him in the hidden lair.

As Kylo and Rey duel aboard the wreckage of the Death Star, Leia becomes one with the force and passes out of the physical realm forever. Both Kylo and Rey feel this in the force and are staggered, their duel temporarily halted. Rey recovers first and uses this to her advantage by taking Kylo's lightsaber from him and stabbing him in the chest with it. She then uses her newfound healing powers to heal Kylo enough so that he won't die, but not enough to enable him to pursue her. It is during this time that Kylo has a vision of Han Solo who tells him that it's never too late to return to the light.
Kylo is deeply affected by this and discards his red saber along with the identity of Kylo Ren. For the rest of the movie, he is now Ben Solo.

After her duel with Kylo, Rey returns to the island of Achtoo determined to do as Luke did and and remain there a hermit. She is upset because she keeps tapping into her anger and causing sometimes almost fatal results that could kill her friends as well as her enemies. Being a descendant of Palpatine, she fears the darkness inside her and what the future may hold if she were to fall.
She scuttles her ship and goes to toss her saber in to the sea when a familiar hand grabs it in mid air, keeping it from falling to the coast and rocks below. Luke Skywalker has returned in force ghost form to counsel and encourage her. She leaves the island in Luke's old X-Wing and heads off to rejoin her friends( or maybe to Palpatine's lair ).

It is said that the throne room will be based on Ralph McQuarre's drawings from ROTJ, with the big giant throne in said paintings.

Ben Solo arrives after Rey, walking in to the giant arena filled with cloaked Sith loyalists with NO weapon. Palpatine drains the life force from him and then shoots force lightening, causing Ben to fall down into a huge abyss. Ben Solo is dead.

Previously, some alien had asked Rey for her name and when asked about her family, she told him that she didn't have one. When asked again toward the last scenes of the movie, Rey tells her inquisitive new friend that her last name is Skywalker. Rey has adopted the Skywalker name in honor of Luke and Leia.