In Just Imagine, the future of 1980 is depicted as a towering, 250-story Art Deco version of New York City where the ground level is abandoned in favor of multi-layered suspension bridges and massive skyways. The world is a meticulously ordered technological marvel where traditional human elements like names have been replaced by alphanumeric designations (e.g., J-21, LN-18) and individual cars have been entirely supplanted by personal airplanes and autogyros.

Societal dynamics are defined by a benign but absolute state control; the government manages a marriage tribunal that decides which citizens are "distinguished" enough to marry their chosen partners. This version of Earth is characterized by a lack of traditional labor and domesticity, with meals consumed as single food pills and babies delivered via coin-operated vending machines. Despite these radical shifts, the film suggests a cultural stagnation where 1930s-style social hierarchies and gender roles persist in a high-tech environment.

The film's predictions vary wildly from the actual 1980. While it correctly anticipated the concept of video calling and televised communication, its vision of personal flight for every citizen remains unrealized. The food pill remains a classic sci-fi trope that never displaced traditional agriculture, and the prediction of a manned mission to Mars by 1980 was overly optimistic, though it correctly identified the moon and Mars as the next frontiers for human exploration. Interestingly, the film's prediction of alphanumeric IDs mirrors the rise of Social Security numbers and digital databases, albeit in a far more literal and oppressive fashion than occurred in reality according to retrospective critiques.