If we had the technology to travel to an exoplanet at a significantly faster speed than the speed of light, it is theoretically possible that we could arrive at the destination before the light from that exoplanet reaches Earth. This concept is known as "seeing into the past" or "outrunning light."
In such a scenario, there is a possibility that the exoplanet could have been destroyed or significantly altered after we departed from Earth but before we arrived. We would not have received any information about this destruction because the light, which carries information from the exoplanet, has not reached us yet.
However, it's important to note that the current understanding of physics does not support faster-than-light travel, as it conflicts with the theory of relativity. According to our current knowledge, the speed of light is an absolute limit, and it would take an enormous amount of energy to approach or exceed it. Thus, until we develop a deeper understanding of physics or discover new principles, faster-than-light travel remains speculative.
Nonetheless, if such technology were ever realized, precautions and observations would need to be made before embarking on a long journey to an exoplanet. Scientists would likely gather as much data as possible about the target exoplanet, including its current state, through observations using telescopes and other remote sensing techniques. This data would provide valuable insights into the conditions of the exoplanet before undertaking a long-duration space travel mission.
Additionally, advancements in astronomical observation techniques and the study of exoplanets are constantly improving our ability to understand these distant worlds. It is unlikely that we would be completely unaware of any significant events occurring on an exoplanet before embarking on a journey towards it.
In summary, while the hypothetical scenario you presented raises interesting questions, the current understanding of physics and our limitations in observing and understanding exoplanets make it highly unlikely that we would encounter a drastically different exoplanet due to its destruction or alteration during our journey.