EW has posted an exclusive first look at Pacific Rim: Uprising including screen shots and more plot details from John Boyega. The story details give more info on the characters including Jake Pentecost's (Boyega) and Mako Mori's (Rinko Kikuchi) relationship and what's gone on since the first filmincluding how the kaiju can return. There is also some more info on the new Jaegers as well. Click here to read the full article, warning possible spoilers. Below is some details from the article.

Jake Pentecost
“Jake is the prodigal son,” Boyega tells EW. “He is a young guy who was on the cusp of greatness in his early days when he was training to be a Jaeger pilot, but he always had a troubled relationship with Stacker.
Father and son fell out, he says, “because of Stacker’s attention and hope and faith in Mako rather than him.” Mako is the Jaeger meister who helped save the world last time, played by Rinko Kikuchi, who returns for the sequel.

The Kaiju
“The Kaiju have found a new way,” Boyega says. “They are way more intelligent than we thought they were. The monsters you saw in the first movie were the test run, to see how the planet would hold up. The breach we thought was closed is not their only way into our world. Their plans are more specific.

About the Jaegers
Gipsy Avenger (center, foreground): “She’s an upgrade model form Gipsy Danger in the first movie,” Boyega says.
“She is still a two-man Jaeger and has new weapons and technology. The new Gipsy has LCD screens and holographic imagery of what is going outside. Her gravity sling has improved,” he adds. “Pilots are no longer locked into robot by feet. It has a scanning system that makes the drift easier to handle. Gipsy Avenger is strongest and hardest to operate.”
Saber Athena (far left, in orange): “She’s the fastest Jaeger, and she is agile and assigned two skillful pilots who know how to do martial arts,” Boyega says. “She has two swords she can join together to slice stuff down. She’s flexible and very fast.”
Guardian Bravo (far right) in red: “She has big electric whips, but is very stocky and strong,” Boyega says.
Bracer Phoenix (background, center): “She is a mystery rogue Jaeger, but is really strong and advanced,” Boyega says. “She has guns on the chest. That Jaeger is, in fact, a three-man rig — one is in the cockpit shooting missiles and bullets from the chest.”

Legendary and Universal have revealed the first synopsis for Pacific Rim: Uprising ahead of NYCC where there will be a panel with cast members and new trailer revealed. The synopsis does give some plot details we didn't know previously. Check out the synopsis below, warning possible minor spoilers.

The globe-spanning conflict between otherworldly monsters of mass destruction and the human-piloted super-machines built to vanquish them was only a prelude to the all-out assault on humanity in Pacific Rim Uprising.

John Boyega (Star Wars: The Force Awakens) stars as the rebellious Jake Pentecost, a once-promising Jaeger pilot whose legendary father gave his life to secure humanity’s victory against the monstrous “Kaiju.” Jake has since abandoned his training only to become caught up in a criminal underworld. But when an even more unstoppable threat is unleashed to tear through our cities and bring the world to its knees, he is given one last chance to live up to his father’s legacy by his estranged sister, Mako Mori (Rinko Kikuchi)—who is leading a brave new generation of pilots that have grown up in the shadow of war. As they seek justice for the fallen, their only hope is to unite together in a global uprising against the forces of extinction.

Jake is joined by gifted rival pilot Lambert (The Fate of the Furious’ Scott Eastwood) and 15-year-old Jaeger hacker Amara (newcomer Cailee Spaeny), as the heroes of the PPDC become the only family he has left. Rising up to become the most powerful defense force to ever walk the earth, they will set course for a spectacular all-new adventure on a towering scale.

Pacific Rim Uprising is directed by Steven S. DeKnight (Netflix’s Daredevil, STARZ’s Spartacus) and also stars Jing Tian, Burn Gorman, Adria Arjona and Charlie Day.