May I suggest that, if it is possible, the current version is automatically (and recursively) added somewhere to posts, so that it is fairly obvious what version a previous thread is talking about? Perhaps a popup warning if the post that you are replying to is for a previous version. Older posts can be checked simply by comparing the date by version release dates.
When a release occurs, topics that contain stuff that was implemented, should be summarized and not locked (the bug may return or something). That would do the trick. Information about version will be pretty useless when release cycle will be short.
