Taylor Swift is a business.Yes, in the future it could be higher. It depends on where the company is going. Artists get less popular over time and alot of assets would then necessitate scaling down, and be offloaded. If the person Taylor Swift decides she does not want to be associated with the business anymore it could lose alot, if she died probably the opposite would be true for a while. Yes a considerable amount of revenue would probably be coming in for the foreseeable future.

Tldr: Past performance is no guarantee of future results. A billion dollar company is already an amazing feat and it is impressive if Taylor can keep the ball rolling at that scale.