Early Tuesday morning, DC Comics tweeted that writer Brian Michael Bendis had signed an exclusive "multiyear, multi-faceted deal" with the publisher, meaning that he will soon depart his long-time home at Marvel Comics. Bendis swiftly retweeted his new employer, writing, "This is real. I love you all. Change is good. Change is healthy. I am bursting with ideas and inspirations. Details to come! Stay tuned!"
Right now, the specific details about Bendis' transition from Marvel to DC are unknown. Acquiring Bendis gives DC access to the writer's specific set of skills and may indicate the company's plans with regards to representation going forward, though at this point it's unknown what properties he'll work on. However, the move will have some pretty major, near-immediate repercussions for Marvel, as the writer has been a key player in the company for almost 18 years, helming major events and creating a number of popular characters.
There's no clear timeline at this point for when Bendis will make his move. Marvel's January solicitations bill him as writing Invincible Iron Man #596, Spider-Man #236, Jessica Jones #16 and Defenders #9, and none of the descriptions for these issues seems particularly terminal. It's possible that Bendis will leave before finishing those arcs, receiving credits as a co-writer or for story, but it's not yet clear if that will happen or even if the series themselves will continue on with different writers after his departure. In an interview with the New York Times, Bendis indicated that there's no ill-will in his move from Marvel to DC, so it's unlikely he's going to abandon the publisher with several half-completed arcs.
Additionally, January solicitations for DC don't indicate that Bendis will start on any particular book then, though there could be a surprise announcement. As comics typically need to be pre-ordered several weeks in advance, it's possible that the company wants to do more publicity for the superstar writer's first project, so there's little reason to believe that Bendis won't get the opportunity to finish up his current Marvel books.