The antonym for the phrase "becomes threadbare" is "becomes brand new." This refers to clothing, fabric or even a situation that once looked old, worn and shabby but has been restored to its original or better condition. For instance, when we talk about brand new clothes, they are free from any wear and tear, and they look fresh and new. The same applies to situations, where they can become more revitalized through necessary changes. With a different perspective and approach, a once threadbare situation can become revitalized and full of life, providing new opportunities, and thus, lead to a brand new outcome.