This paper examines the trajectory of a spectacular change in the development of future temporal reference in Brazilian Portuguese over five centuries. Focusing on four competing exponents of futurity, we show how the incoming form gradually expropriates the preferred contexts of the older variants, prior to ousting them from the sector. These results confirm that the transition period in linguistic change is not abrupt, but proceeds as a series of small adjustments, as incoming and outgoing variants jockey for position in the system. As a variant recedes, constraints on its selection do not remain constant, though the distinctions it conveyed may be transferred to another exponent. These findings challenge some widely-held assumptions (i.e., that change affects all contexts simultaneously, or that the grammar remains invariant during the course of change).