The PCAT is a normed test, so the percentiles will not change. For example, to get into Mensa you need to score at the 98th percentile of the population on an IQ test. These tests change regularly, but regardless of the score, you will still score at a specific percentile which earns you admission into the club. So, if a pharmacy school requires at least an 80%, that will not change. If anything, the school may raise their standards because of competition, but that doesn't have anything to do with the test itself.