This from collider which they pulled from the wrap:
The report notes that conversations are in very early stages, and the actual size of Keaton’s role is up in the air. But essentially, the actor’s presence is a way to introduce the idea that there is no “main” DC Universe, just many branches on one tree. So the same universe that saw Keaton’s Batman do battle with Jack Nicholson’s Joker exists, as does Christopher Nolan’s Dark Knight trilogy universe, as does the universe in which Arthur Fleck (Joaquin Phoenix) became the Joker, etc etc. Reportedly, Keaton’s presence won’t at all effect The Batman, Matt Reeves’ upcoming film that sees Robert Pattinson putting on the cape and cowl.
The report notes that conversations are in very early stages, and the actual size of Keaton’s role is up in the air. But essentially, the actor’s presence is a way to introduce the idea that there is no “main” DC Universe, just many branches on one tree. So the same universe that saw Keaton’s Batman do battle with Jack Nicholson’s Joker exists, as does Christopher Nolan’s Dark Knight trilogy universe, as does the universe in which Arthur Fleck (Joaquin Phoenix) became the Joker, etc etc. Reportedly, Keaton’s presence won’t at all effect The Batman, Matt Reeves’ upcoming film that sees Robert Pattinson putting on the cape and cowl.