The WWE will remain popular because there will always be fans of fighting. It is entertaining for me to watch any form of violence. It is based on men asserting their dominance over one another and while women enjoy it too, I feel like men will be the ones to keep it popular.
People like to see violence. One person fighting another until a winner is chosen. For this reason the WWE and others like it will remain until a time when people no longer want to see fights. The blood and injuries only add a level of excitement to the fights, and the want for a winner.
People will become more cynical in the future and have higher entertainment standards. People may still be impressed by strongmen but will have no tolerance for sporting fraud, especially with the use of drugs increasing in professional sportsmanship. Also, I think it's traditional working class white audience will diminish over time.
I think the WWE will always have a core group of fans but I do not think they are now nor will the every be popular for the long run. The majority of us are not interested in the WWE and we never will be. There's nothing they could do to intice large groups of the population to watch because it's just not that interesting.