The deer that live on Yggdrasil don't symbolize life, the Yggdrasil itself symbolizes life. Also, the region is based of France, and the myth itself is from Europe, so as slim as the chance that Xerneas and Yveltal are inspired by Norse mythology, I'd say it's not as slim as the Japanese one. I doubt they'd make a guardian of the forest when Celebi already exists and has that exact description.
I don't get what you mean by Special typing being false? Fact : Fire, Water, Electric, Psychic, Dark, Grass, Ice and Dragon were all Special types. Fact : We've had Fire, Water, Electric, Psychic, Dark, Grass and Ice eeveelutions. What part of this is false? If patterns were to continue the next eeveelution we would have gotten would've been Dragon. And if Fairy were to placed in Physical or Special base, it's pretty obvious it's be Special. Yes this is all speculation, but it was never "confirmed false".
So the Sylveon movie was released and no new Eevee, in my book that just makes it less likely, but never impossible. And we were never told that Sylveon "is the only new eeveelution", it's just highly unlikely.