user128: If you are like me, the majority of manga (not so much anime) I read are on hiatus. 
But, is asking about the production off-topic?
What do you mean by upcoming, or hiatus manga/anime?
'Hiatus' means that production of the manga/anime is paused, and will be resumed at a later date. Some manga, like NANA, Highschool of the Dead and D.N.Angel (and many others, I'm sure) are on hiatus and have not been updated in such a long time it's almost easy to assume they won't ever be updated.
Alternatively, if a manga-ka has announced that their manga is going to be made into an upcoming anime or if a manga-ka has said that he/she is making another manga series - it would be considered to be upcoming in production. The point I'm getting to about upcoming anime/manga is: is it OK to ask about key aspects or dates of the release of a particular anime/manga?
How could this be on-topic?
It seems like questions relating to the production of anime could be on-topic for the following reasons:

The subject is directly linked to Anime/Manga
The answers can be factual and have details about the plot (that can be used for future reference etc.)
For an anime and manga Q&A site, it seems reasonable to ask about upcoming manga and anime.

Example questions:


Does anyone know when [title] will resume production?  
Is this [title] discontinued, and why?  
When is [title] going to be released as an anime?  
Will [title] become an anime?  


Thanks :)

user93: I think that questions about when something would resume production or when it would be made into an anime should be off-topic. The questions would become obsolete as soon as the date passes and as such would be pretty much useless. Also, as Logan M said, if you can't find the answer yourself, nobody will be able to.
Even asking if something will become an anime should be off-topic because it's either a relatively easy yes-no question or a question where the answer may become obsolete. The answer can change, making the previously correct answer wrong.
Only unchangeable, plot-related questions should be allowed, and these types of questions generally don't fit under that category. I think for related questions that don't fit under the descriptions in my previous two paragraphs shouldn't necessarily be flat-out called off-topic but should have to have unchangeable, plot-related answers to be on-topic.

user24: We should focus on questions which are answerable factually, and with answers that will remain correct and will not become useless in the future. There are some cases in which such a question about a not-yet-aired series or a series on hiatus would meet these requirements, but in all the example cases you've given, I don't think that's the case. There's also practical difficulty in that the answers tend to either be either very easy to find via google, or nonexistent. So if you can't find the answer yourself, chances are no one else here can. You're still welcome to ask on chat, of course, but by-and-large these don't make good questions for the main site.
For an example of a question that I think would be acceptable (not necessarily good), one could ask "Which novels are going to be animated in the Monogatari Series Second Season anime?". The answer to this is more-or-less known, and is very unlikely to change. It would also not be totally useless even after the series airs. There's some practical difficulty because you won't always know whether the question is answerable, so I'd advise against these questions unless you're sure an answer exists.

128: <p>If you are like me, the majority of manga (not so much anime) I read are on hiatus. 
But, is asking about the production <strong><em>off-topic</em></strong>?</p>

<h2>What do you mean by upcoming, or hiatus manga/anime?</h2>

<p>'Hiatus' means that production of the manga/anime is paused, and will be resumed at a later date. Some manga, like <strong><em>NANA</em></strong>, <strong>Highschool of the Dead</strong> and <strong>D.N.Angel</strong> (and many others, I'm sure) are on hiatus and have not been updated in such a long time it's almost easy to assume they <em>won't</em> ever be updated.</p>

<p>Alternatively, if a manga-ka has announced that their manga is going to be made into an <em>upcoming</em> anime or if a manga-ka has said that he/she is making another manga series - it would be considered to be upcoming in production. The point I'm getting to about upcoming anime/manga is: is it OK to ask about key aspects or dates of the release of a particular anime/manga?</p>

<h2>How could this be <em>on-topic</em>?</h2>

<p>It seems like questions relating to the production of anime could be on-topic for the following reasons:</p>

<ul>
<li>The subject is directly linked to Anime/Manga</li>
<li>The answers can be factual and have details about the plot (that can be used for future reference etc.)</li>
<li>For an anime and manga Q&amp;A site, it seems reasonable to ask about upcoming manga and anime.</li>
</ul>

<h2>Example questions:</h2>

<blockquote>
  <ol>
  <li>Does anyone know when [title] will resume production?  </li>
  <li>Is this [title] discontinued, and why?  </li>
  <li>When is [title] going to be released as an anime?  </li>
  <li>Will [title] become an anime?  </li>
  </ol>
</blockquote>

<p>Thanks :)</p>
 93: <p>I think that questions about when something would resume production or when it would be made into an anime should be off-topic. The questions would become obsolete as soon as the date passes and as such would be pretty much useless. Also, as Logan M said, if you can't find the answer yourself, nobody will be able to.</p>

<p>Even asking if something will become an anime should be off-topic because it's either a relatively easy yes-no question or a question where the answer may become obsolete. The answer can change, making the previously correct answer wrong.</p>

<p>Only unchangeable, plot-related questions should be allowed, and these types of questions generally don't fit under that category. I think for related questions that don't fit under the descriptions in my previous two paragraphs shouldn't necessarily be flat-out called off-topic but should have to have unchangeable, plot-related answers to be on-topic.</p>
 24: <p>We should focus on questions which are answerable factually, and with answers that will remain correct and will not become useless in the future. There are some cases in which such a question about a not-yet-aired series or a series on hiatus would meet these requirements, but in all the example cases you've given, I don't think that's the case. There's also practical difficulty in that the answers tend to either be either very easy to find via google, or nonexistent. So if you can't find the answer yourself, chances are no one else here can. You're still welcome to ask on chat, of course, but by-and-large these don't make good questions for the main site.</p>

<p>For an example of a question that I think would be acceptable (not necessarily good), one could ask "Which novels are going to be animated in the <a href="http://www.animenewsnetwork.com/encyclopedia/anime.php?id=15054" rel="nofollow">Monogatari Series Second Season</a> anime?". The answer to this is more-or-less known, and is very unlikely to change. It would also not be totally useless even after the series airs. There's some practical difficulty because you won't always know whether the question is answerable, so I'd advise against these questions unless you're sure an answer exists.</p>
