How would that kill gmail? It's not like they're going to lose any real part of their user base. Short of a press release from google confirming the behavior, the average user is not going to go through the hassle of finding a replacement provider and then changing every email address associated with every service they use (if it's even possible for the service) all for some nebulous and impossible-to-confirm conspiracy theory put forth by tech experts and security experts that don't get listened to even when there is proof. And it's not like other companies and services would take a stand by ceasing to offer service to customers with gmail accounts- that's an incredible way to lose a vast portion of your customer base.
I wish it weren't this way, but I just can't see that bringing down gmail. Especially not when every google service requires a gmail account- probably the same one most people have had for years.