Can someone collect all info supporting this idea?
Basically this is it:
We have the tweet from the GI editor guy (or whoever it was that worked on GI) that the cover of the next GI issue (which is the August issue, which we will see the cover on in July) is going to "make fantasy fans crap themselves". Looking at a number of recent fantasy games, we can see that most are either already announced, probably going to be announced at E3, or aren't going to be heard of for some time. This means TES V has a bit of a larger chance to be on that cover, but, of course, its all speculation.
As for being unveiled at QuakeCon, it is because Zenimax now owns Id software, and Bethesda has expressed a desire to be present at QuakeCon to make it a joint venture for all Zenimax owned companies to show off their games and to make it a convention to really show off all their stuff. If Bethesda is committed to this, we should see them at QuakeCon with something to show, and there's hope that rather than just show off games they're publishing they'll also unveil a big game to really hit the point home that QuakeCon is a big event.