The antonyms for the phrase "becoming fact" are numerous. Some words that convey the opposite meaning include false, untrue, inaccurate, unreal, and fictitious. These words describe something that is not based on reality, but rather is imagined or fabricated. Other antonyms for "becoming fact" could include things like conjecture, speculation, or rumor - all of which suggest that something is being discussed, but without any definitive evidence or proof. Ultimately, the opposite of "becoming fact" is simply something that has not yet been proven or validated, and therefore remains in the realm of fantasy or uncertainty.