I don't necessarily foresee widespread rioting and killing of whites. I think there will be the usual smattering of opportunistic black "flash mobs" who will pick off isolated whites when they can find them.
Even feral blacks are beginning to figure out that white Americans have had it with them. In the 60's, weary whites signed on to social programs designed to pay blacks to stop rioting and burning cities, but we no longer have the money and millions of unemployed and underemployed whites are no longer so tolerant and forgiving as before. We've heard decades of "white privilege", blah, blah, blah.
That tactic doesn't work any more. Read the "comments" sections on most of the Zimmerman trial news sites. Whites are finally finding their nerve and their voices and calling this outrage what it really is: An anti-white political show trial.
The real issue has never been white racism, but black rejection and contempt for the norms of civilized behavior, most especially for the rule of law.