Not unless something decisive happens at the hearing. A routine court date where no final decision is rendered does not result in release. He will be transported to court, the hearing will take place, and he will be returned to the facility the same day. The release date stays at October 11.
The only scenario where a court appearance leads to immediate release is if the judge takes action that ends the incarceration, such as dismissing the charges, ordering time served, or issuing a sentence that results in immediate release. If the September 15 date is a routine status hearing, a continuance, or any other procedural step without a final ruling, nothing changes and he comes home on October 11 as scheduled.
If there is any possibility the September 15 hearing could result in a significant ruling, his attorney would be the one to ask about that.