the older generation of vectors, like word2vec, compress to one sense of a word, but even if we ignore polysemy, opposites have a lot in common. So for any antonym pair, they would not be minus-1, they would be actually pretty close.

The big challenge is when we go beyond antonyms with clear scales like heat, speed, size. To me "as of now" is recent, and therefore opposite to "old". I would like a word other than "opposite" or "antonym" or "contrast" that captures a wider range.