Most Salafis will inevitably burnout - unless they are hopeless cases.
I think the Salafi side of Islam will eventually completely burn out or become radically different from what it is today. Infact, much of Islamic extremism and terrorism are desperate attempts to retain this aspect of the faith. Stoning, amputations,triple talaq and gender apartheid have as little place in today's world as racial apartheid, and barring some unthinkable catastrophe, the eventual complete abolition of these is almost an inevitability.
In more and more nations, even Islamic ones, the laws aren't the laws of Islam and things allowed by Islam are prohibited by secular laws, there's American movies, and T.V. shows, Western clothes worn by youngsters and even Japanese anime and Hindi movies in Pakistan, all challenging the traditional culture, and barring a rare Yvonne Ridley, there are few takers for the comprehensive Islamic way of life.
Salafi extremism, the attempt to mark oneself from others by way of dress, terrorism are all protests against this inevitable destruction of their culture and way of life.
The Salafis of the future will either be non existent, or else a tiny minority like the Orthodox Jews, devout in their daily life but having completely given up Shariah laws,and the rest of Muslims and Muslim nations will be indistinguishable from others.