The show is written by English screenwriter and playwright Jack Thorne, based on an original story co-written with Rowling and John Tiffany, who is directing the play.
Given the millions of fans around the world, the decision to move the characters on two decades is potentially risky.
"Some fans do not wish their own ideas of what happened to be compromised," said Catherine Horvath, senior news editor at fan website The Leaky Cauldron.