The correct answer is that scientific ideas are always open to revision.
With the discovery of Coelacanth, it is clear that the knowledge, which is developed by science is always open to revision and question. None of the scientific ideas is ever proved once-and-for-all. Science is continuously looking for new proof that could reveal issues with the present understandings.
The ideas, which are completely accepted at present times may get modified or rejected on the basis of the new proof discovered in the coming times. For example, until 1938, the paleontologists accepted the fact that coelacanths got extinct about 80 million years ago.