Please do not unless you ask on chat or flag for a moderator. We would rather help edit it if you have any doubts if it will be on-topic. The reasons why are listed below, but if your question revolves around speculation or items that will be clear the day after launch, please hold these questions until the experts can answer them with authority and on the record.
Kyle Cronin's answer about Mountain Lion seems to apply fully here to questions about other pending versions as well.
While it is possible that there is a question about [generic future OS] that would be appropriate for this site, the overwhelming majority of [generic future OS] questions will be closed because
[generic future OS] is not yet a shipping product, and as such, its features may change before it ships. Any questions answered about the current state of [generic future OS] could easily not be accurate by the time the product ships. As such, these questions are too localized.
Questions about what features it will contain in the future when it is released are speculative; no one knows (not even Apple engineers) what the final shipping version of the product will be. So questions asking about what features will be in the final version are not a real question that can be answered.
Questions about the specifics of [generic future OS] are in most cases unanswerable except by people who have signed a Non-disclosure Agreement. Both the answerer and the site could get into trouble if we allow answers to be posted here that violate such an agreement.
The small set of questions that ask about publicly available information tend to be both localized in time (not relevant once the product actually ships) and lend themselves to a very short answer. Questions like "Has Apple publicly announced a timeline for the next version of iOS?" do not violate an NDA, but really lend themselves to a one-sentence answer; these are not the sorts of questions we want to encourage on this site.
While questions will be considered on a case-by-case basis, I find it unlikely that any [generic future OS] questions posted in the near future will remain open on the site. If you have a counterexample of a question that invites a long answer, is likely to be stable even after the software is complete, and can be answered without risking violating an NDA, I'd love to hear about it, but I remain skeptical that a good question will emerge.