First reported by the Daily Mail and confirmed by Deadline, Sheeran is in talks to join the film about a man who wakes up to discover he's the only one in the world who can remember The Beatles' songs. That's the most detailed plot description we've heard thus far. There's some dispute whether Sheeran would also be contributing music but he will definitely have an on-screen role. I have to imagine he'll provide new music to the soundtrack, as well.
If all goes well he will be joining Baby Driver's Lily James, Himesh Patel, and Kate McKinnon who is still in talks.