Good question. This is something I covered extensively in this thread with some of my thoughts on the subject. The rule will generally go that you can post new answers to old questions if the existing one(s) are incorrect, or if you can add substantial new detail to the answer that is helpful and relevant to the topic.
However, the situation you're brought up is a bit different. I briefly touched upon this in the thread linked above, but I guess I should've explained what "reservation" should be made if the answer is simply outdated. I might not speak for Pokemaster here, but I would personally advise posting a comment on the answer as opposed to adding a new answer. Some questions that fit into this category could be updated any number of times based on new game releases or other changes, which would end up being an obvious disruption to the site. For that reason, posting a comment would be better for the site's organisation, in that it won't bump the question up in as many different pages, but would bump it in the full activity area so it can be discussed if need be.
I'm also of the belief that the answer to the question should link with when the question was made to maintain consistency, so posting a new answer might disrupt that. Though this shouldn't prevent the question from being up to date since it might be accessed again by players looking for answers for the current generation. So I think the comment is a fair balance between the two. Let me know if you have any of your own ideas as to how this could be handled.
