Bloch-Boltzmann transport theory fails to describe the carrier diffusion in current crystalline organic semiconductors, where the presence of large-amplitude thermal molecular motions causes substantial dynamical disorder. The charge transport mechanism in this original situation is now understood in terms of a transient localization of the carriers' wave functions, whose applicability is, however, limited to the strong disorder regime. To deal with the ever-improving performances of new materials, we develop here a unified theoretical framework that includes transient localization theory as a limiting case and smoothly connects with the standard band description when molecular disorder is weak. The theory, which specifically addresses the emergence of dynamical localization corrections to semiclassical transport, is used to determine a "transport phase diagram" of high-mobility organic semiconductors.