Few people will forget the first time they saw the original Avatar in 3D, the gorgeous, verdant alien rainforests of Pandora popping out of the screen as if every viewer in the auditorium had just been fitted with 31st century tech upgrades to finally allow ourselves to see the full picture. And yet pre-release hype for James Cameron’s forthcoming sequel to the highest-grossing film of all time, Avatar: The Way of Water, has been bogged down with a general sense that we have seen this all before, that a return to the world of the N’avi is less exciting than it was in 2009, when Cameron’s fantasy epic seemed primed to usher in a whole new universe of stereoscopic film-making.

At Saturday’s D23 panel for Disney offshoots Marvel, Lucasfilm and 21st Century Fox, audiences were treated to the world’s first glimpse of actual footage from the movie itself. A giant Cameron – the film-maker is currently in New Zealand finishing the movie – gazed down from the big screens on an auditorium of 7,000 people at the Anaheim Convention Centre in Southern California, while cast members Zoe Saldana (Neytiri), Sam Worthington (Jake Sully), Sigourney Weaver and Stephen Lang talked about the new movie’s focus on the importance of family. Then the footage was unleashed, and all of a sudden we were reminded of exactly why Avatar made such a buzz in the first place: that glorious supercharge to the senses that comes from 3D film-making zooming above the stratosphere.

The sequel takes place after Jake and Neytiri are forced to flee their forest home for the coast following the return of Lang’s perfidious Colonel Miles Quaritch to Pandora - sort of. One scene revealed our first look at the new Quaritch, who has been restored to life in the body of a N’avi Avatar after getting multiple arrows through the chest at the end of the last film. Another witnessed several N’avi children frolicking in the Pandoran ocean, amongst spectacular marine fauna, while a third saw the same characters in what appeared to be a human base, seemingly discussing the events of the previous movie before they were born.

The Way of Water seems to have slightly hamstrung itself with an unwieldy storyline in which Quaritch is not the only character returning from the dead. Sigourney Weaver’s Dr Grace Augustine has been reborn as Jake and Neytiri’s teenaged daughter Kiri in the new film - you might remember her consciousness appeared to be downloaded into the sentient tree worshipped by the N’avi (stop laughing at the back!) at the end of part one. There’s also a human character called Spider who seems to suffer from guilt as the son of one of the original defeated invaders from Earth last time out.

It wasn’t easy to piece together much of the film’s plot from the limited footage shown, but then Avatar’s success was never about the story, and it was hard not to be wowed by the incredibly photorealistic fantasy imagery. Cameron may have spent a decade getting the movie right, and has rather missed a trick by casting a mo-cap N’avi version of Lang, rather than the sneering, leering, pop-eyed real deal. But once all the barbs about Ferngully and Dances With Extra-terrestrial Wolves have been banished, it’s likely we’ll all sit down to watch the sequel with something approaching the awe that greeted the technological wonder of its predecessor.

Other highlights of Saturday’s panel included the appearance of an unusually emotional Harrison Ford during the Lucasfilm section, the 80-year-old actor taking to the stage alongside co-star Phoebe Waller-Bridge and director James Mangold to discuss the upcoming fifth Indiana Jones film. A key takeaway was the movie’s apparent title: out in June 2023, it seems to be called simply Indiana Jones. Ford said it was the last time he would play Henry Jones Jr, but described the new film as “fantastic”, and praised Waller-Bridge’s performance.

Footage suggested that the film will be partly set in the 1940s, with a younger version of Indy (though crucially still played by a de-aged Ford) once again taking on the Nazis. Waller-Bridge’s character, Helena, is described as a “foil” to Indy and seems to appear during the section of the film in which the intrepid archeologist is an older man.

The main highlight of the Marvel section of the panel was exclusive footage from the upcoming Black Panther: Wakanda Forever, in which it is revealed that the Earth’s nations have decided to try their luck at stealing some Vibranium from the technologically advanced African nation, apparently in the belief that they will no longer be at risk from getting duffed up by Chadwick Boseman’s King T’Challa.

The studio took the decision to kill off the title character following the death of Boseman from colon cancer in 2020, and cast members Angela Bassett, Winston Duke and Letitia Wright all paid tribute to their lost colleague from the D23 stage. In the footage, it looks like western nations have got it pretty wrong if they think Wakanda is in a weakened state: badass members of the country’s all-female Dora Milaje special forces turn up to easily shut down the attack, and Bassett’s Queen Ramonda regally parades the interlopers at a United Nations style international conference.

Marvel wasn’t ready to show footage from its upcoming Thunderbolts film, but the appearance of Stranger Things actor David Harbour, aka the Red Guardian, drew one of the fan event’s largest roars of approval. For the first time it was revealed that the movie, Marvel’s answer to DC’s Suicide Squad, will feature a team of antiheroes comprising Red Guardian, Hannah John-Kamen’s Ghost, Wyatt Russell’s US Agent, Olga Kurylenko’s Taskmaster, Florence Pugh’s Yelena (Black Widow’s pugnacious little sister) and Sebastian Stan’s The Winter Soldier.

Marvel boss Kevin Feige told the audience: “It tells you everything you need to know about the Thunderbolts that the Winter Soldier is the most stable among them.” And indeed the movie, directed by Robot and Frank’s Jake Schreier, looks like it could have a hell of a time explaining how such an unhinged bunch of morally-comprised superheroes can possibly work together for the greater good. It ought to be fun finding out.

• This article was amended on 12 September 2022 to correct the surname of the Stranger Things actor David Harbour.