Unfortunately, young Bill Denborough actor Jaeden Lieberher didn’t participate in the above interview, so it’s unclear who he would choose for adult Bill.
Elsewhere, Sophia Lillis suggests Jessica Chastain for adult Beverly Marsh, while Chosen Jacobs picks Chadwick Boseman for adult Mike Hanlon.
From an acting talent standpoint, all of the above suggestions would probably be great choices, although many are definitely long-shot picks.
IT is a tale set in two time periods, one where the Losers Club’ battle the titular monster as children, and one where the group reunites to fight IT again as adults.