How actors relate to the future has long been considered important in research on the governance of transformations towards sustainability. Recent contributions have explored the politics at play in the ‘making’ of futures and the forming of collective expectations. Building on the concept of socio-material incumbency and integrating academic discussions which appreciate the politics of future-making, we consider the forming of collective expectations as a process through which prevailing socio-material arrangements are challenged and reproduced. We introduce the concept of ‘scope incumbency’, through which the particular ideas about the future collectively deemed plausible are shaped by prevailing power arrangements. Consequently, we suggest it plays an important and underappreciated role in the reproduction of locked-in systems. We illustrate this perspective by exploring how mobility futures are imagined in sustainability transition research. We investigate academic contributions which explicitly articulate possible, plausible and/or desirable alternative mobility arrangements and consider the extent to which and how contributions challenge and reproduce hegemonic socio-technical orders. We find that a substantial portion of the contributions collectively limits the scope of the plausible around automobile-centric futures in several ways.