Is saying "I will become such and such," or "You won't be able to do that," or "Such and such won't happen" considered claiming knowledge of the unseen?

The Unseen is known only to Allah, as He states: "Say: None in the heavens and earth knows the unseen except Allah," and "And with Him are the keys of the unseen; none knows them except Him." As for a person saying, "I will become such and such," or "You will not be able to," or "It will not happen," out of optimism or an expectation based on signs, this is not claiming knowledge of the unseen.