I don't believe that is possible within Community, however it is possible if your business also has a SMM service. Publishing via the Reach (Social Publishing) part of SMM gives you the ability to have an approval flow.
The on community blog management is quite simplistic and needs an overhaul. You can't even see drafts by other users without either switching to their user account (if you are an admin) or if they give you a direct link to the article.
