If the VGAs have live streaming available to an international audience that is still one significant advantage over Game Informer - Both the Oblivion and FO3 unveilings were GI exclusives so it was a month before the international audience had something more substantive than a fan overview. Of course Bethesda could always go with multiple magazines as they did with FONV or do an online unveiling so the VGA's advantage doesn't seem to trump it's small viewership.
Also, even last year if I recall correctly the announcements that did happen at the VGAs weren't too shabby. I'm pretty sure Batman: Arkham Asylum (2? I don't keep up with it) and maybe even Halo: Reach and Call of Duty: Black Ops may have been revealed at last year's event, and they certainly had no trouble getting sales. Having big names like these will inevitably attract reporters and such for gaming websites and magazines alike to tune in. Even if these reporters are only in the US, the news if TESV were announced at the VGAs would spread over the internet like wildfire.
So I guess what I'm trying to point out is that the question should not be 'how many people will be watching the VGAs?' but 'who will be watching the VGAs' in which case I think the event would be a prime place to light the spark and watch the fire spread.