I also think it's silly when people see the skeleton remains in breath of the wild like the one in Eldin. Clearly those remains are Levias, you cant doubt that.
Like I said I havent beaten the game, however I have all 4 beasts complete and the master sword, Im only holding off going to Ganon because I want to get all the shrines and quests complete because I heard you cant play the game again to complete everything once you beat the story mode, so can...
Well for starters, some armor descriptions (like sheiks headwear, OoT/WW/TP links outfits) mention these specific characters from past games, meaning this game takes place in the future of those games.
Wolf link is also summoned by the amiibo, the loading screens that give you tips mentions...