Personally question shouldn't really need to be edited. using Code Geass as an example the question "Is Lelouch dead or alive after R2" is fine regardless if R3 existed or not.
though i would agree to edits to update where a question talks about the general end of the series when a new season of the series is exists eg.
- "is Ed trapped in our world at the end of the Fullmetal Alchemist anime" => "is Ed trapped in our world at the end of the 2003 Fullmetal Alchemist anime series" after Fullmetal Alchemist: Brotherhood came out
- "What happened to Hei at the end of Darker than Black" => "What happened to Hei at the end of Season 1 of Darker than Black" after Darker than Black: Ryuusei no Gemini came out
Answers on the other hand are trickier because we shouldn't be rewriting other people's answers. so
- if you're own answer is outdated you can edit it with an updated answer
- if you know an answer is outdated you can comment on the answer to let the poster know that it's outdated for whatever reason
- you can post a bounty. there is a reason when setting a bounty which specifies outdated answers and wanting something more up to date
- you can post a new updated answer and possibly link to an existsing answer saying something like
[USER]'s answer was accurate/correct at ##/##/#### however since Season # new information contradicts this
there should really be no need to be making edits to other people's answers saying something like
This question was posted ##/##/### which at the time was correct as there was no Season #
because all non-community wiki answers have the date of when the answer was posted.
and personally when i answered Code Geass questions i did so after the series was finish1 and wouldn't want people updating my answers themselves while the season is on-going, which as we have seen with a certain Dragon Ball Super answer when users start trying to update information based off the last information that was just aired which is quickly contradicted in the next episode (also the answer was made before Super was conceived in the first place)
unless it was a community wiki answer it should have been an edit with the answerer deciding if they should update it then or wait until it's been confirmed
1: don't bother pointing out the Julius Kingsley thing. i am aware of that and thought the OVA was finished when i posted. i did update my answers when i learned a new OVA was out which revealed who he actually was