This is a good question. It is probably best to start with a little history. The United Nations was started in 1945, after World War II to hinder wars from taking place. It also replaced an older organization (League of Nations), which proved to be ineffective; World War II was proof of this. The main benefit of the United Nations is to provide a forum where dialogue can take place, so that through diplomacy there would be peace among nations.
Now as for the future of the United Nations, no one can tell. However, here are some points to consider. First, a place or an organization where nations can meet to discuss matters of state is imperative. So, there is a need. Second, war has always been a part of human civilization. So, even on this level, there is a need to hinder wars from taking place through diplomacy. Third, the United Nations also conducts humanitarian aid to various nations and this, too, is needed.
In light of all of these points, I would say that the United Nations will be needed and hence survive. As for how effective the United Nations will be, I am hopeful, but not very optimistic. As the economy worsens, nations will be more protective of what is theirs. There are challenges ahead. In this context, if the United Nations fails to keep peace and bring a positive benefit to nations, then it will come to an end, just like the League of Nations.