I know this sounds very un-Nintendo but I really think they could announce Wii U Zelda at VGX Awards this weekend. Reggie and Nintendo are attending and seem to have something up their sleeve. They never, ever attend VGAs and the fact that they're going out of their way to do so seems to indicate that they know they need to get the "VGA Audience".
Any Nintendo announcement, like Mario Kart 8 or DKC release dates would seem sort of out of place in a show filled with Uncharted, Fallout (maybe), and other darker IPs which are likely to dominant the broadcast. Add into this the fact that Nintendo has said they did plan to reveal the game at E3 and then at NY Comic Con, they seem like they want to show it off show.
Perhaps they'll release a teaser trailer aimed at the VGA crowd this weekend during the show? I know that isn't something Nintendo typically does but hey, the Wii U's doing badly so why not try something new? I don't know if it would really help anything but I can't think of any Nintendo announcement having any impact at VGX except Zelda U.