As new evidence emerges, hypotheses and theories are rejected and modified. Actually, evolution is both fact and theory. A fact is a verifiable 'truth'. Evolution is a fact. Organisms have changed over time and will continue to change.
Evolution is change or descent with modification.
As a theory, evolution explains how and why things change over time. The theory of evolution elucidates the mechanisms of change. Hence, the theory of evolution is a tentative, modifiable, and falsifiable explanation of how organisms change over time. Some characteristics of science and scientific explanations are important to keep in mind. Note that scientific and non-scientific endeavors are vastly different.