When in the question bank, I suggest making it a requirement to note the most recent generation needed for the question in the tags, or none, so that we can later sort posts by generation and also not worry about outdated information, that or include it as a separate prompt in the post somehow. So it would look something like this:
Q. What are all the items that help boost gastrodon's speed?
A. It's the item item item item thing
The generation would say GenV in the tags or the separate prompt so that when gen VI rolls by and there are new answers, we know which questions we can run back to in order to know which ones would be outdated.
I know that we can simply post the new information on old questions, but the biggest problem is that they will already have answers and will be difficult to track down aside from just manually running through older questions.
The second suggestion would be to add an "outdate" flag to posts, similar to the regular flagging. Only instead it is used for information that is no longer relevant to a certain generation.