Traumatic brain injury always permanent?

No: A person can have full recovery. The best time to tell what will be permanent is those symptoms still present after one year. A few predictors of permanent damage is how much memory is lost and the length of being unconcious or if there was lack of oxygen for a prolonged time.

Depends on a lot: This is often the debate which engages forensic neuropsychologists (see http://forensicneuropsychology.Com) and forensic neurologists. Results can vary greatly even with similar ct or MRI findings. Generally severity, presence of intracranial bleeding, elevated icp, early or especially post-traumatic seizures, locaiton of injury, shearing, and pre-injury factors ie. Age, prior injury, health etc.

No: it depends on the cause, location, amount of injured brain. Concussion is a mild brain injury. Most people recover from mild injury frin trauma, even from stroke.