I think you're starting to see the effects of some societal trends that started in the 60's really take hold, and this lack of good up and coming, believable in action movie... male stars is definitely part of it.
See the problem is, most sort of manly man types who can be convincing as a character that is shown being generally competent and powerful, strong and confident... well, the type of guys who can convincingly portray that can do so because at least to some degree, they ARE that in their real life.
But what percentage of guys who are like that, are also pursuing acting careers? Acting isn't generally something those types of guys gravitate toward. This problem only gets worse as young boys have fewer such actors to idolize and want to emulate. Some of the action stars who are just now ending their viable life cycle probably looked up to people like John Wayne, Sean Connery, Steve McQueen, Clint Eastwood etc etc as they were growing up, and this in turn inspired them to become actors.
So all the following have to happen to get such an actor:
1.) You have to have a child raised to embrace the masculine (happening less and less)
2.) You have to have that child see masculine actors to idolize in movies as he grows up (happening less and less)
3.) You have to have that person actually go through with the desire to pursue acting (small percentage)
4.) You have to have them actually be able to get to a point of being a decent actor, and able to learn how to do that. (Most can't)
5.) Lots of luck has to happen too, the right role for their career to take off... etc
The pickings are slim and will get slimmer.
That's part of why they keep using Cruise, Willis, even Schwarzenegger. Because the younger generations just aren't providing those sorts of men to replace them. It's also why more and more actors are being brought from Australia, or other countries that haven't been QUITE as hard hit by these same societal trends... and being asked to play these characters with an American accent, etc.
Thanks a lot feminism!