In the original game, the Future was an apocalyptic time period in the near future when Fuse has nearly conquered the world. Planet Fusion was closer to Earth than in The Past, and most areas found in the Past were destroyed after having been flooded by a sea of Fusion Matter. In addition, the liquid Fusion Matter seemed to had eaten away at the rest of the surface, putting the infected sea at a lower elevation. Certain areas of the Suburbs were connected by fragile wooden bridges between island-like areas, which are all that are left of the FusionFall universe in its time period.
In the Future, Sector V and more predominantly Peach Creek Commons had become the main hub and base of Fuse's resistance, and also where most special events were held. Most of the transportation systems were destroyed, as the Slider System fell to pieces in Genius Grove; only two S.C.A.M.P.E.R.s and four Monkey Skyway Agents remain for the player's travel. Apart from the Tech Square tutorial, there are just five accessible infected zones with three Fusion Lairs among them, spread across eight areas. The Candy Cove Infected Zone, sunk below the ground, just half of Candy Cove itself eroded from Fusion Matter. On the other hand, the infection in Sector V's KND Training Area, which was the only place not shielded off in the past, grew into an Infected Zone.
It is unkown how much of this will be changed in Legacy, though when looking at the major changes made to the Future's Tech Square (Different landscape, locations, aesthetic features, and infected zone), it is safe to to say that the rest of the Future will also have very large changes made to the same sort of features.