Reasons I believe that BotW takes place on/parallel to the “Era of Decline” {Pre-LoZ}
Physical decline of the Kingdom seen, even before Ganon's attack 100 years ago. Zelda is confirmed to be researching the "ruins" of the Kingdom in the latest Famitsu leaks.
Presence of Ganon itself, and a given history of this character actively acknowledged by several NPCs, i.e., the Old Man, and an elderly woman's voice (Impa?) from the Switch trailer.
The presence of several diverse races: Zora, Goron, Rito (confirmed!), Korok, Hylians, and Sheikah. Meanwhile, the humans live in a post-apocalyptic state, scattered across the land…
The Sheikah tribe has been scattered, their monks awaiting the hero underground; their technology was banished by the King and is effectively defunct… until the hero awakens them with his Sheikah Slate.
The lay of the realm of Hyrule is a very realistic, very open-air world, heavily influenced by the original The Hyrule Fantasy: The Legend of Zelda (Famicon/NES) video game, which started it all… For example, both Over-worlds sport a sea to the east and south, mountains ringing in the north and western frontiers, green forests and clear lakes in the centre and southern realm, with the source spring coming down from the NE…
The Calamity Ganon is an overwhelming threat to Hyrule, barely contained by the Sheikah’s technological prowess within Hyrule Castle… if this beast were to break free, the world would end up in a state even more like the world presented in The Legend of Zelda: overrun with monsters, no settlements, people driven underground, and a Demon King with the power of the gods…
March 3, 2017 is coming fast. Bring it on!