The VOIDRUNNER'S CODEX is coming! Explore new worlds, fight oppressive empires, fend off fearsome aliens, and wield deadly psionics with this comprehensive boxed set expansion for 5E and A5E!
Given the points in Eric's rumor, my guess would be the announcement wouldn't be made at GenCon, whenever it's made.
I will even will speculate that the reason it won't be is because they know it will be a very unpopular announcement. Rather than have GenCon being a hotbed of complaints and negativity, I suspect they will release the info elsewhere (Dragon? Website?)
It's bad enough they're gonna get bombarded by people because of the 4E rumor. I'm sure we'll hear something unofficial, if only to calm the masses. The good thing about rumors like this, WOTC has a chance to get fan reaction in advance about what we DON'T want.
It'd be funny to see the negative reaction if they did announce it. When 3E was announced in 1999, the place went wild; I remember the hooting and joyous cries (and I still have the nifty t-shirt). This time, they'd be bombarded with booing and quite possibly thrown food.