How to handle answers made obsolete by a change in real life circumstances?

Question

In a rare scenario of some (real-life maybe) events leading to the answer becoming obsolete, what should the answerer do? What should the moderators do?

The question that got me thinking is this one. Well, it probably should have been WebApps SE question indeed, but one can come up with a hypothetical RPG example:

1. The RAW question is asked about B.
2. The answer is given that would be considered correct for the current state of the rules.
3. The author of B browses the SE, sees the question and realizes that the logical RAW contradicts the RAI.
4. The author publishes the errata and provides his own answer.

Answer 1

This is going to be a fairly rare circumstance. When they do though, generally they take care of themselves as the usual voting practices kick in: answers that are now incorrect usually get voted down, and that either pushes the answer down the page or inspires the author to update or delete it.

In this case, since you're the author of the relevant answer, my advice would be to just delete it. The answer's content doesn't have any value to preserve anymore, and there's not much you can do to update it without just duplicating the other answer.