LEAKS YO
Or not, really teases, but good ones this time! So I'm just gonna use this board to sperg on about shit, as usual. So it was just announced that a whole slurry of things are planned for 2017, most notably, several new characters, and a truly advancing plot, thanks to...
Now, alongside this, we have the return of Saint Celestine, who, for space saving purposes, I'll not show a pic of her new model. As well, a new mechanicus character has appeared, named Belisarius Cawl,
According to rumors, he's a Magos who's been working on a super secret project for over 10,000 years, making him one of the single oldest living members of the Imperium, sans the Emperor, if true.
All this connects together in the next image, which was given alongside a hint that the plotline /may/ be that Celestine is returning, heading a Black Templar crusade meant to penetrate the cadian gate, likely after its announced fall.
In this image, connections form between a few of the new characters, including that qt inquisitor girl I forget to mention, as well as an as of yet unannounced (As far as we know) character in the background, in the red, eldar like armor.
Now is the time for personal theories. So, given the image itself, we first notice the bright blue hue which typically denotes the inside of the webway, and the presence of the eldar-like character, presumably a dark eldar due to his spikey armor, we can assume that for some reason, this black templar crusade force is being lead through the webway by this dark eldar ally. Now, one may wonder why the DE would ally with marines. I think that Belisarius is the connection here. Being a character present during 30K times, it can be presumed that his secret research may have something to do with the webway, maybe even the imperial webway project. As well, in a recent codex, it was shown that a Mechanicus/Inquisitor sect recently visited the Dark Eldar capital of Commoragh, to seek their help in bolstering the golden throne, and that a dark deal was struck between the two parties.
So in the end, I think this is something of an extension of that deal, the newly realized human/DE aliance using the webway, now available to them through the DE, to make a surprised strike at Cadia, meant to break Abaddon's renewed offensive, which appears to have now fully taken the world. /end fantheories
Oh, there was also this video, so more info on the seventh!
Edit: Found a bigger version of the above image, but it's got shit written all over it, so here.