What is the function of the past in visions of the future? For critics, futures built on recycled futures-past, at best, signal a failure of imagination and, at worst, foreclose much-needed alternatives. Against a backdrop in which the future is predominantly thought of as a threat, this paper offers a more nuanced account of the entanglement of past and future at lieux de futur, complex assemblages of imagination, relations to time, scales of the past, forgetting, and sense experiences. Utilizing fieldwork at the 2018 Future of Everything Festival and collected materials from Astana Expo 2017 this paper reconsiders the function of the familiar in visions of tomorrow through the concept of déjà vu (promnesia). Triggered by a single familiar element among what is presented as novel, déjà vu activates a sensation that one can see the future unfold before its full arrival. Promnesic futures thus act as a prophylactic against broader looming threats (e.g. climate change) by rendering them seemingly navigable.