Though the greasers won the rumble, are their problems with the Soc's over in "The Outsiders"?

Of course not.  The Greasers have accomplished nothing that will make any real difference in their lives by winning the fight.  They may feel better temporarily by having 'beaten' their social enemies, but nothing has been done that will effect the social and economic inequalities of society at large.  The social attitudes that seperate the Greasers from the Soc's are not surmountable by punching one another.  Ponyboy grasps this instinctively, as does Johnny when he hears the news.  The only things that will change one's life are decisions made internally, the decision to "stay gold."