Minecraft releases weekly snapshots, which allow players to view upcoming features pretty much as the developers develop them. Since anyone can get their hands on these, they are not considered speculative. However, since they are not considered "released" these features often change, leading to questions and/or answers which are often specific only to certain unreleased snapshots.
One recent question is this:
Does horse-armour degrade? Does horse armour lose durability like with the player wearable armour? Is it repairable or enchantable?
It's a good question, but is extremely localized since many of the answers are likely to change from week to week as the developers flesh out the feature since it focuses on an in-development feature.
Are Minecraft questions about an unreleased feature too localized?