This is the 17878th most frequent Russian word.
устанут
"Устанут" means "will get tired" in English.
The word 'устанут' here is used in the future tense to describe the action of becoming tired, which is anticipated after the mentioned activity.
После долгого рабочего дня они устанут.
After a long workday, they will get tired.
In this sentence, 'устанут' is used to predict the tiredness of students as a result of a challenging activity.
Я уверен, что студенты устанут после такого сложного экзамена.
I am sure that the students will get tired after such a challenging exam.
Here, 'устанем' (from the same verb 'устать') is used in the conditional to express the outcome of prolonged activity without rest.