Before Tiber Septim became Emperor, Cyrodiil was a jungle. He transformed it into a temperate climate. Do you think Cyrodiil will be a jungle in ES:O?
Also in this timeframe, I seem to recall the Tsaesci ruling the Empire. Now, it could be set after that was dissolved, which it probably is, because the trailer talks about noone on the Imperial Throne. What do you think?