The situation is similar to that described here. A poster asked a question, I answered it, and then he changed the question to better reflect what he meant, making my answer incorrect / irrelevant.
However, the difference is, that rolling back the OP's edit is not appropriate because after the post was reworded to match what the OP was asking, other people answered the new question. What should I do with my answer in such a case? Simply delete it, along with the comments that it is incorrect?