I worked on the trauma floor of a hospital for a few months last year and many of my patients were there due to a recent traumatic brain injury (usually as a result of a motor vehicle accident or fall of some kind). These injuries are life changing not just for the person injured, but family members as well. Some people would give up everything (social life, hobbies, job) and go completely broke to take care of their loved one. It was super heartbreaking to see.
Sounds like Mr. Jansen is making pretty good progress so far though. We use a 1-10 level scale (called the Rancho Los Amigos if you're interested) to measure brain function/activity during recovery from a brain injury and from what they said in the video it sounds like Jansen is around Level 5 now (out of 10 levels). Progression to the next Level 6 includes being able to recognize loved ones again, so hopefully that is not too far off in the future for him and his family.
The rate of recovery for brain function is fastest and most significant in the initial weeks/months after the brain injury. After that, the rate of recovery slows down significantly and improvements in ability to do "new" things are fewer and farther between. Unfortunately Mr. Jansen is pretty up there in age and his brain isn't as likely to adapt/fully recover as a person in their 40s or 30s that experienced the same injury, so the odds of a full recovery are already against him. Hopefully he is able to make it to a point where he is able to live on his own with only periodic help from a caregiver that checks in on him. Even in the best case scenario though, this injury significantly reduces his lifespan.
With all that said, screw these dudes so much. The entire situation was completely avoidable. Even if Jansen did throw the first punch and "start it", there was nothing keeping the GX guys there or requiring them to engage with him. They had several opportunities to skate away and diffuse the situation, such as when Jansen was first knocked to the ground. Instead they stuck around and continued to hit him while he was down, and then skated away leaving him knocked out without checking to make sure he wasn't critically injured and needing emergency assistance. That's cold man...