In fact, the opposite is true. Since the Big Bang, the steady proliferation of diversity has been the only long-term trend. It predominates in natural ecosystems, and in human communities. Its longevity suggests that it is not going to expire soon. Moreover, if the purpose of the universe does change, and if the change spreads with the speed of light, it will take several billion years before the principle of diversity becomes completely invalid.
Diversity is a matter of survival and prosperity.
For example, genetic diversity enhances resistance to disease and adaptability to a changing environment. In the absence of diversity, the universe would become an infinite expanse of uniform space, indiscernible from a perfect vacuum. We cannot preserve diversity unless we know what it is, and how to measure it. The definition seems accurate, but it does not provide a good yardstick with which to measure diversity. It is more convenient to define diversity as a complexity of systems.