There is foreshadowing in this story in what happens every time George and Lydia go into the room in the first parts of the story. We know (having read the whole thing) that they are going to end up being killed in the room. We can see this foreshadowed when they go look at the room earlier in the story.
When the do this right at the beginning of the story, something has been killed, which may foreshadow that they will be. More obviously, the lions charge them and they feel like they have barely escaped with their lives. This foreshadows what will actually happen to them.
Then, later on, we see George go into the room and find his old wallet. That is more foreshadowing. Something similar will happen to Lydia later.
There is immediate foreshadowing in the opening lines of Ray Bradbury's "The Veldt":
'George, I wish you'd look at the nursery.'
'What's wrong with it?'
'I don't know....I just want you to look at it, is all, or call a psychologist in to look at it.'
With this last line of Lydia Hadley (whose name, interestingly, has the past tense of have as part of it), there is a sense of foreboding, not just for the parents, but also for the children since there is the suggestion that they are psychologically altered by this virtual reality of the African jungle. The impending danger is foreshadowed in, not only the charging lions, but more subtlely in the "green-yellow eyes" of these virtual animals, whose evil influence supercedes the parental one. For, the children now have become obsessed with their virtual world, rather than the real one: "They live for the nursery."
Written in 1972, Bradbury's story not only foreshadows the destruction of the family unit of the Hadleys, but it hints at the dangers of virtual reality that are a present threat to the detachment of people from friends and family in modern society.
"The Veldt" originally appeared in the Saturday Evening Post in September, 1950 and foreshadowed television's influence on the American family unit. FYI