It will not have been worth the sacrifice if we destroy the earth or a multitude of species go extinct before we get to an alien planet.
That comes down to opinion (begging the question). One's opinion could be yes if they believe intelligence or sentience to be the prime trait that confers moral worth to a being.
Natural selection and natural disasters are responsible for more destruction and death (we just call it "Change") than humanity can ever accomplish by happening to be the dominant species of the planet. On the other hand we do actively work against the destruction/deterioration of Earth, and even keep many species of animals that would go extinct without us in the game for a little while longer.