Oh wow your right I feel dumb. I need more sleep.
Still think its the Wind Waker timeline, but if it is it would have to be far after Spirit Tracks since it would've had the ocean dry up first which would mean its likely not a previous Link. The placing in the timeline is hard to pinpoint and I love it. So mysterious!
I think the Wind Waker connections are pretty strong, but with the Temple of Time, Hyrule Castle Town, and other elements, I don't think the adult timeline is where BotW falls. I'm still leaning towards it being the bridge between OoT and LttP, fleshing out the 'fallen hero' timeline beyond just a jumbling of the earlier 2D installments.
- The Master Sword being referred to as 'The Master Sword of Resurrection', and the presence of a 'Resurrection Chamber' is pretty telling. It would properly explain how a Hero is brought back after being defeated.
- The Deku Tree being present is still possible WITHOUT it being in Wind Waker's timeline. Technically, the 'Fallen Hero Timeline' represents everything that happened in the Adult Timeline, just that the end result is different: Link loses during the final battle on top of Ganon's Tower. This means the Hero of Time would have still purified the Forest Temple, the Deku Sprout would have still emerged, and grown into a new Deku Tree. The Deku Tree recognizing Link, but not vice versa, would mean this would have to be the Hero of Time in BotW.
- For the same reasons listed above, Koroks being involved doesn't necessarily mean it's automatically in Wind Waker's timeline either. After Link's defeat, there would still have been plenty of time for the Kokori to evolve into Koroks, and it's never specifically stated that the reason for their change was due to the Great Sea, merely that they 'gave up their human forms in favor of flight'.
That means this would put this either during, or maybe after, the Imprisoning War (or Sealing War), centuries before A Link to the Past.
OR I'm completely wrong, and they really are making this a pre-Great Flood game between OoT and WW, which would have to have the most depressing ending ever.