It sucks to get injured, especially right before the season. Or during the season. Or any time really, it's never fun. As for recovery, it just depends. Most pain and injuries get better within three months. Groin strains are usually back within 2 weeks, but can take 2-4 (longer if it's a grade 3). Hamstrings 2-7 weeks. Patellofemoral pain gets better within three months, but there are a subset of people that still are not returned to sport in a year. Subacromial shoulder pain (aka rotator cuff related shoulder pain aka formally known as shoulder impingement) gets better within three months, but there are a subset of people that will have pain for over two years. Back pain typically gets better within 2-6 weeks, the list goes on.
All that to say that yes, the majority of things do get better. It's just frustrating when it happens right before a season. Hopefully the athletic trainers and the doctor will have a good plan of action for him.