Excuse me bumping this up, but I do think we should have a response to these questions in some way. We can't really have questions without an answer on the site. I think something should be formalised, however I agree with Pokemaster that there is no way we can enforce a rule on this. Instead, we can compromise.
The simplest way to deal with these questions is to edit them so that they don't ask for something we don't know. I've been doing this for a few months now, and it has worked well so I thought I'd put it out there as an option. For example, questions can be changed like this:
"When will Marshadow release in the west?" → "Do we know when Marshadow will release in the west?"
I could take down the question on the left, but I don't really have grounds to do that because there's no rule. Instead, I would change it to the question on the right. That one is a yes or no question, and we can answer it right now even though the Pokemon Company has been so quiet on the subject. If the answer was yes, then it would basically be courtesy to mention when Marshadow releases as well. All of that can be dealt with in comments or as a follow-up question regardless.
I can't see anyone having a problem with that as opposed to having the thread removed entirely, so I think this is a good way to handle these. If you see posts like this around, I'd encourage that you edit them if you can, or flag them so somebody who can edit will get around to it. I would leave a comment for the asker as well so they know what is going on.