So after the newest trailer, I've been thinking and developed a theory about how the game may start out. Potential spoilers if I'm right, but I'm honestly probably not.
My theory is that BotW actually starts out with a pre-apocalyptic Hyrule judging by the start of the trailer. However, something happens (bird people?) and the Hyrulians developed the guardians to protect them. However, things go wrong (Ganon) and the world comes crashing down.
Now my idea is that you start out as Link in the pre-destruction world and actually can run around doing the tutorial section of the game. Then all the above happens, and the game starts in the state we saw at E3.
This could provide a super cool intro where we see and can actually interact with a Hyrule at peace, where Link fights petty bandits or troublesome groups of goblins to start, and is seen as a hero who already conquered a great evil before.
Tldr: We play as an already victorious Link for the tutorial in a peaceful Hyrule, and then all goes to hell and the actual game starts with Link waking up after his cryogenic stasis stuff.
Discussion started at here by BaconCheesecake