One event that is foreshadowed is Emily's future refusal to part with Homer Barron. Earlier in the telling of the story comes the passage where Emily's father died. Her reaction when people come to the house to get her father's body is interesting:
"Miss Emily met them at the door, dressed as usual and with no trace of grief on her face. She told them that her father was not dead. She did that for three days."
Finally, she breaks down and lets them take her father's body, but, her reluctance to part with her beloved father, even if he was dead, directly foreshadows the entire Homer Barron situation that we discover at the end. Another instance of foreshadowing is when Miss Emily buys the arsenic. That foreshadows Homer's death. She goes to the drug store, asks for arsenic, and when the pharmacist asks why, it states,
"Miiss Emily just stared at him, her head tilted back in order to look him eye for eye, until he looked away and went and got the arsenic and wrapped it up."
Here is another instance of foreshadowing; she gets enough arsenic to "kill an elephant" as the druggst says, then refuses to say why she's getting it. One last instance of foreshadowing is the smell that radiates from her house. It is an awful smell, so bad that people sneak into her yard at night to apply lime to try to get the smell to go away. That also foreshadows the horrific discovery at the end.
So yes, even though Faulkner's chronology in telling the story is confusing, and out of order, if you are watching for signs, there are clues to the disturbing ending. I hope that helps!