Never heard of this project. I mean sounds like a cool mod, but why is this news, and why does a mod need to care about a release date? They're not selling a product, they can release whenever lol.
The Fallout 4 script extender will be what breaks after the next-gen update, so the Fallout London team will have to just wait and see what happens and then change the framework before making everything compatible. These problems are why Fallout London's release date got pushed back indefinitely.
They can't release the mod until the Fallout 4 script extender gets updated to work with the update, since (like most mods) they rely on F4SE to add additional capabilities to the game.