It would be helpful for theme developers to have the version number of bblog as body class. That would help in managing themes for publicly released version and upcoming newer version.
Say for example something would change in version 7.4 and current was 7.3. Theme developers could adjust for 7.4 and at the end of the style sheet they could have specific 7.3 rules that would keep the theme working in the 7.3 and when 7.4 launches the theme would work automatically and 7.3 rules wouldn't affect anymore (and could be later easily removed from the style as they are no longer needed).