I think you miss the point of the constitution Peter. It's the bases for all of our laws and freedoms here in the US. It is not the full and complete details, but an outline to be followed. It is the constitution that created the 3 branches of government which work very well together as a system. And when new laws are created by the legislature it is the job of the Judiciary to make sure they fall within the confines of the constitution. It is the basis for all laws and freedoms. And since it is the foundation, it will never be outdated.
Just read the Preamble to see why it will never be outdated...
We the People of the United States, in Order to form a more perfect Union, establish Justice, insure domestic Tranquility, provide for the common defense, promote the general Welfare, and secure the Blessings of Liberty to ourselves and our Posterity, do ordain and establish this Constitution for the United States of America.