Here we are a month away from Blizzcon and many appear to be preparing for a potential inundation of black and white samurai bears or some remnants of their forgotten land. As all of this discussion was derived from the discovery of a trademark filing back in August, I thought it might be appropriate to actually ask an ex-attorney I work with who is knowledgeable in the field of trademark filings as to what this filing actually means and share some insight to coincide with our rampaging speculation.
Essentially all the filing means is that Blizzard has simply filed to preserve the right to use the name "Mists of Panderia" for one or more of the variety of electronic outlets that were listed in the filing and any potentially accompanying contests (giveaways, Mountain Dew sponsored activities, etc.) that Blizzard might have in accordance with the release of whatever this actually is. Just because there are several items listed for use, (discs, mouse pads, etc.) that does not mean they will actually use them, they are just keeping that ability to use these outlets themselves. This is not to say that MoP will not be the next expansion, however, it also means that there is just as likely a chance this could indeed be some sort of one-off game (iPhone, browser based, actual game in a box) or promotional item and Blizzard has simply preserved all forms in which this game could potentially be downloaded, sold, or used. Certainly with the naming of disks, mouse pads, etc. in the filing it looks like expansion filings from the past, but it also looks like every other game they've filed a trademark for.
As there is no mention of this being a comic or the like in the filing, I'm afraid the ideas that this is somehow a written item is out of the question unless it accompanies whatever electronic outlet this is, e.g. a guide. Unless the type of item is listed in the trademark filing, it cannot be used so whatever this is it will definitely be electronic in nature. Maybe Blizzard is looking to target a younger audience with something a little more fuzzy than angry gods and fiery dragons spilling their guts, we'll certainly find out soon. I agree with many of the people who have said that this title is not like the others in terms of describing an event or main antagonist and frankly there has been so much opposition to this title that I doubt Blizzard would use it for an expansion. Why title it "Mists of Panderia" and piss off half your player base when you can have the same exact content and call it "Vengeance of the Gods" or some such and make it sound, well, a little more dangerous as is their pattern.
My guess: Blizzard has another title ready to be filed but will wait until the absolute last minute to have the attorneys file it due to the catastrophe that was the Cataclysm leak. At any rate, I hope this provides a little clarity into what is possible and I will try and follow up on any questions this post might produce.
TL;DR: Hold your horses on MoP being the name of or the actual next expansion.