The movie, directed by Rob Marshall, is set 25 years after the events of 1964’s original “Mary Poppins.” If Whishaw’s deal goes through, he would play the grown-up Michael Banks.
Variety first reported last month that Meryl Streep is also in talks to come on board.
David Magee wrote the screenplay, based on the stories by P.L. Travers, with Marc Shaiman composing an all-new score and writing original songs with Emmy nominee and Tony winner Scott Wittman.
Blunt stars as the title character with Manuel-Miranda playing a street lamplighter named Jack. The story will take place in Depression-era London and follow a now-grown Jane and Michael Banks, who are visited by the enigmatic Mary Poppins following a personal loss.
Marshall, John DeLuca, and Marc Platt are producing the pic, which will shoot in early 2017 in London. The movie hits theaters on Dec. 25, 2018.
Whishaw is best known for playing Q in the last two James Bond movies, “Skyfall” and “Spectre.” He also appeared in “The Lobster” and “The Danish Girl,” in addition to voicing the titular bear in “Paddington.”
He is repped by CAA, Peikoff Mahan Law, and U.K.’s Hamilton Hodell.