People who where injured or lost loved ones will be looking to be made as whole as possible by suing the hotel because they are the only entity with deep pockets. How many tens or hundreds of millions does the hotel owe each one of those victims for the actions of a mad man? I saw the video of the shooter taking bags up to his room. There was not even a hint that there were guns and ammunition inside.
This was a terrible tragedy, but I'm not sure anyone should be held financially accountable for not preventing it. That said, MORALLY, MGM should use some of their considerable financial resources to help the victims.
Also, if it were my company, I would create a memorial at the location while still maintaining it as a concert/event location. And I would invite all the surviving victims and their families to return for a concert on the next anniversary of the shooting. Massively increase security, celebrate music, life and love, and show the world that we will not allow violence to cow us. I would attend.