The SAT does not test how well you will do in life. It is not a good indicator of how smart you are, because everybody has different skills and abilities, and it marks you down for something you may not be good at. I think the SAT is pretty unfair to kids who want to go to college and get a degree, but can't because their scores are not good enough to be accepted.
The point of a SAT is to gauge whether a person gained enough knowledge to successfully be able to use college to continue their education, and how much help and furtherment they should receive according to how much was is there. Sure, you can make different tests, or maybe modify the SAT, but as of this moment it is still a good test, simply because there are not really any amazingly better alternatives to the SAT in that regards at this very moment.
Although the SAT has gotten flak for being one of the dreaded 'standardized tests,' tests are something that all colleges use. In order to do well on the SAT, one must study thoroughly and be intelligent enough to get a good score. This is a good measure for how well that person can do in college, and thus should not be eliminated.