There are many issues that will be important in American government in the relatively near future. Let us look at some of them.
One is the issue of when any of the current Supreme Court justices will retire (or die) and who will appoint their successors. The Court has been divided relatively evenly between liberals and conservatives. The next appointment or two might change that balance dramatically. The oldest three justices are 80, 77 and 76 (will be 77 on July 23, 2013) years old. These people might retire or die in the near future and that could lead to a major change in the makeup of the Supreme Court.
Another issue is that of demographic change as it relates to partisan politics. As America becomes less white, will the Republican Party be able to adapt? Up until now, the Republicans have relied heavily on white votes. Will they be able to expand their appeal?
In foreign policy, a major issue will be what happens with Iran and nuclear weapons. This is perhaps the most immediate threat that we can see that might lead to a war.
These (and many others) are issues that are or will be important in the near future.