A screenshot of the leaked page was shared on Twitter by lashman - which you can see below - and more details were posted on ResetEra too. This is called Commander Lilith & The Fight For Sanctuary, due to arrive on June 9, and we even get an official description:
"Return to the award winning shooter-looter for a new adventure that sets the stage for the upcoming Borderlands 3. Sanctuary is under siege, the Vault's map has been stolen and a toxic gas is poisoning Pandora. Fight new bosses, explore new zones, get new loot (including an entirely new tier beyond Legendary) and join up with Lilith and the Crimson Raiders to take on a deranged villain hell-bent on ruling the planet."
"Returning players can pursue an increased level cap of 80, while newcomers can automatically boost to level 30 and dive straight into the action."