A violation for what? Parole? Probation? Who is "they" that is trying to send him to prison? Does he have new charges? Has he been convicted in the new case?
With the confusing facts you've provided, it's impossible to give you a meaningful answer. His attorney would have all of the information and is in a much better position to answer any questions.
There are certain time periods for the courts to take action, but it depends on whether the case is a felony or a misdemeanor, and the stage of the case -- whether it is before a trial date, or after a conviction. If he hasn't been convicted yet, then he can't be sentenced yet. If he HAS been convicted of a felony, he has the right to be sentenced within 20 court days of the verdict or plea.