I think things have already happened. I can't begin to list the number of peculiar incidents that have had "no terrorists links." The most memorable was the plane that crashed into Queens...ala a shoe bomber.
It seems like things have also happened in Memphis. My friend is a nursery school teacher and an arabic child was in her class. This family was pretty nice and friendly to everyone but did not speak english well. They showed up at neighborhood gatherings with a video cam taking pictures of everyone. They didn't participate, eat, or talk with anyone. Just kept smiling and taking pictures. A few days before 9-11, she called them about the first day of school. They said that something had happened and they had to move out of the country very soon. She told them that their son's belongings (nap mat, blanket, stuffed animal, etc....) were still at the school and asked when they wanted to pick them up. They said to keep it or throw it away but they didn't have time to pick it up. She thought that was strange for parents to not care about their child's naptime favorites. Then 9-11 happened and neighbors told her that this family left alot of their belongings behind when they quickly moved out of the country. She reported this to the hotline number for suspicious activities. But no one ever called her back. Then the doctor who was an expert on contagious diseases was in Memphis for a conference, and one night after dinner, he just jumped into the Mississippi. The Flyer also did a story on this suicide/accidental death and the strange deaths of other experts all over the world.