It's really interesting reading all the information coming out of rugby right now. It's changed so much over time.
From my memory it went.
Concussion can kill you but if you get up with no symptoms you're fine. If you have symptoms wait until they go away then you're fine.
If you get a concussion and get up and you are fine but have another concussion shortly after you can die. You just need rest and then you are fine.
If you don't get knocked out you might still have concussion.
Repeated concussions can cause permanent damage and that damage can stack and make you more prone to new ones.
You can get brain damage from non knocked out big hits. This can manifest itself years later
Then when shit really hit the fan. Basic bog standard training sessions where you have no negative symptoms can cause brain damage if you do them too often. This is where we are now. Maximum contact training is in place. Players are getting g force sensors in their gum shield.
I can see this going futher to having longer breaks in games with recovery periods. They have changed the rules a about as much as they can. Head guards will probably be mandatory soon.
Finally the game might even die. But I expect the risk of brain damage when managed is less than the pros that come partaking in the sport.