The victims would sue Mandalay Bay regardless of the time line. Also Jason Aldean, the concert promoter, the concert security, the city of Las Vegas, and any other deep pockets that were in the state at the time.
That’s not to say the hotel mishandled the situation. Plenty of people bring plenty of luggage into Las Vegas hotel rooms every day for trade shows and other events, and nothing prepared anyone for this shooter’s actions. But lawyers gonna sue.