It seems evident that Mr. and Mrs. Hadley were eaten by the lions from the veldt scene that plays on the walls of the nursery. This is foreshadowed by such events as Mr. McClean finding Mrs. Hadley's bloody scarf on the nursery floor and Mr. Hadley finding his chewed and bloody wallet there. The last we see or hear of the Hadley parents, they are in the nursery, watching the lions come closer. Then they scream.

When Mr. McClean comes to the nursery, the children are sitting placidly watching the lions feed. He is worried because the parents are missing. Wendy asks him if he'd like a cup of tea, but we have to expect that he too will be devoured by lions or another predator from the veldt.

As for Wendy and Peter, we have to expect that they will be eventually taken by social services—or that they too will become the prey of the lions.