What are some text clues and predictions for "A Sound of Thunder"?

You can predict the ending based on the comments about changing the future and the discussion of who is president.

You can make a prediction that the men are going to change the future from the fact that such a big deal is made about how careful they have to be because it is easy to change the future.  In the beginning of the story, they discuss who the president is.  This is a text clue that foreshadows the ending, when another man is chosen president.

“We’re lucky. If Deutscher had gotten in, we’d have the worst kind of dictatorship. There’s an anti-everything man for you, a militarist, antiChrist, anti-human, anti-intellectual. People called us up, you know, joking but not joking. Said if Deutscher became President they wanted to go live in 1492. …”

This foreshadows the ending when Deutscher is president.  In the present, Keith has been elected and they are happy because certain people feel that Deutscher would be a tyrant.  At the end of the story we will see the spelling on the sign is different and Deutscher is president.

Another example of foreshadowing is the caution about how easy it is to change the future by changing something in the past.  The government regulates time travel carefully, we are told.  There is a special path, and you do not step off that path!

“We don’t want to change the Future. We don’t belong here in the Past. The government doesn’t like us here. We have to pay big graft to keep our franchise. A Time Machine is finicky business. Not knowing it, we might kill an important animal, a small bird, a roach, a flower even, thus destroying an important link in a growing species.”

These text clues indicate that someone is going to step off the path to change the future.  All of that talk about not changing anything in the future definitely foreshadows Eckels stepping off the path onto the butterfly.  He changes the future, just like we have been warned against.