Based on everything I feel like the Master Sword is a lost ancient artifact, and the game will revolve around trying to locate and pull the Master Sword for at least the first half, hence why the logo places so much emphasis on the sacred grove. The damaged condition of the master sword could have to do with Demise's energy being released (strongly implied he's sealed in the master sword at the end of SS) which would explain why Calamity Ganon exists and exists as a phantom. Very likely this Ganon was killed previously and the condition of the sacred grove, as well as references to the ancient sea and Hylia worship, seem to peg this as being Zelda 3 chronologically.
Bird guy is probably gonna be a hyper evolved Loftwing r oyal servant on par with the Shiekah aka basically Fokkas by any other name
EDIT: just realized it looks like they're imolying the guardians protected the castle. Extra defenses would make sense after Zelda 1 where Hyrule was all but completely destroyed by Ganon's rampage
