This question already has an answer here:
I remember speaking to a moderator in chat once where they told me that a question about a future release which is currently in-development is actually on-topic here as long as what is posted is not a bug report. Though I have seen many people ignore this and actually the close reason description, and give this:
Bug reports and problems specific to development version of Ubuntu should be reported on Launchpad so that developers can see, track and fix these issues.
Even if it is not an issue which should be reported on LaunchPad as it is not a bug report.
However when I went and posted this question How to install the new GNOME Software app on 16.04 for testing purposes? I immediately got 3 close votes, though it is not a bug report which should be reported on LaunchPad, nor something which cannot be answered, and as this answer does not fully cover this instance and I can't find the place in chat where the moderator told me this, I thought I would post this question just to get this clarified, is it on-topic to ask questions about future releases when you question is not a bug report, and can be answered, and maybe is even answered as a self-answered Q&A?