wordpress-3.1 but surely not down to the revision level?
The initial aim of the wordpress-3 tag was for help with features and functions that were added in, well, WordPress 3. Now their meaning is more of a catch-all - there are a worrying amount of questions with just a wordpress-* tag.
I'm not entirely convinced anymore about the usefulness of version tags in any form.
They've become somewhat of a virus. Easy to catch, difficult to remove.
Version tags are indeed a problem. I can imagine some limited cases where it would be useful to tag a question with a version number, but the majority of questions currently don't need that tag.
We already discussed this before, with the suggestion to change the
[wordpress-] prefix to a
[version-] prefix, and being stricter with these tags, but this was not (yet) executed. Perhaps it is time to ask this again, now that we "graduated" to a public site?
It seems that you're experiencing the same issues I have administering SharePoint Overflow. We use major version tags.
For most products, this version number is really important. A lot changes between major versions so answerers will often ask the OP this again and again on so many questions. So perhaps it makes sense to have a tag for version to minimise this.
However, when/if we make it through the Area 51 commit phase (sorry, shameless plug) and migrate to Stack Exchange, we may want the platform to force users to add additional tags besides just version, to avoid the problem Thomas mentions. I'm often editing questions with just the version tag and no tags describing content.
Now, another way of looking at this is to forget about versions and encourage users to answer questions based on what they know of the platform. So if there is one way to do it in WordPress 2 and another way in WordPress 3, then answerers should describe both (if they know) and make the difference clear. This goes towards one question being the resource to solve a problem. Otherwise you could end up with questions like "How do I do XYZ in WordPress 2" and "How do I do XYZ in WordPress 3" or some other form of noise. This will just make content harder to find.
If this community is just getting started, I'd lean towards the latter.