Here's a quote of George C. Williams (1985. 'A defense of reductionism in evolutionary biology.' Oxford Surveys in Evolutionary Biology 2: 1-27) refuting the claim that evolutionary theory must predict future evolutionary events.
"From this [...] theory of adaptation comes a reductionist methodology [...]. Its practitioners imagine that they understand a studied organism well enough to recognize certain of its features as components of some special problem-solving machinery. If other postulated components are not yet known, it is predicted that an appropriate investigation will reveal their existence. This is the most frequent kind of prediction now being practised in evolutionary biology and it has immensely enriched our understanding of organisms. The idea that a theory of evolution must predict future evolutionary change is unrealistic, but it has been the basis of some prominent criticisms of evolutionary reductionism." (Williams 1985, p. 1, my emphasis)
Actually, I sanitized the quote from references to selfish-genes and the adaptationist programme, because that would only raise the ire of certain folks and thus distract from the content of the statement concerning prediction in evolutionary biology.
Here's the full quote with the formerly deleted words in bold:
"From this selfish-gene theory of adaptation comes a reductionist methodology known as the adaptationist programme. Its practitioners imagine that they understand a studied organism well enough to recognize certain of its features as components of some special problem-solving machinery. If other postulated components are not yet known, it is predicted that an appropriate investigation will reveal their existence. This is the most frequent kind of prediction now being practised in evolutionary biology and it has immensely enriched our understanding of organisms. The idea that a theory of evolution must predict future evolutionary change is unrealistic, but it has been the basis of some prominent criticisms of evolutionary reductionism."
