A probation officer can seek a warrant anytime while the Defendant is on probation. If he is in custody for some other offense and they have not taken a warrant yet he can bond out on the charges. A hold doesn't necessarily mean he cannot get out.
Georgia law provides that a probationer arrested on a warrant for violating his probation is entitled to a preliminary hearing at which the judge will determine whether to hold him or release him with or without bail to await further hearing or the court may dismiss the charge at that time. If the charge is not dismissed at this time, the court shall give the probationer an opportunity to be heard fully at the earliest possible date.
The court doesn't need the warrant to schedule the hearing. An experienced criminal defense attorney should be able to help you with this matter.