With how many leaks for Borderlands 3 there were, you'd start to think they are intentional to build hype, but let's disregard that because there is a new trailer to see.
The official Instagram for Borderlands 3 posted a trailer titled "Borderlands and Chill" which they quickly removed.
There are some interesting things to see, the cooperation of the Iron Bear and other players, some split-screen scenes, a new damage model where certain enemies can be immune, not just resistant to elemental effects, Amara using her Siren powers, a skag following FL4K and Zane using an ability that might be a decoy, or a boost, or invisibility, who knows.
Unfortunately, the Instagram video wasn't up long enough for to us record it, but a YouTuber, Dantics, did manage to save it and he did an amazing job analyzing what can be seen. The trailer begins at the 2:36 mark and after it is the frame-by-frame analysis.