Blogging should be done from an urge to share your thoughts on something. Not from trying to identify an "unexplored niche". This isn't exactly business - at least not for most of us. If you approach this trying to lure and please an audience you're doing it wrong.
This, if the cata details is something you are passionate about then do it, if you just looking for clicks, then doing it will usually show in the writing, people have WoW.com and MMOchamp for all there fixes of beta spoilers, people not checking them wont read it due to Spoilers.
Also what Icedragon said, Making a blog that has a limited lifespam can be a problem.