Apple supporting it won't help apple users one bit, because nobody else uses an actual application to check mails anymore. It's mostly web mail clients everywhere, and they obviously can't use encryption.
iOS? Plus, I know folks who use mail.app. I also bet they could figure out how to instrument Safari with browser-side encryption for their cloud users.
A few more privacy scandals break, and if Apple had an end-to-end encryption story that sounds roughly like: “If you’re using Apple products and services, you probably don’t need to think too much about the techy parts.” I could easily see Apple cementing their position for anyone even remotely concerned about privacy.
Apple the computer company. Apple the media company. Apple the smartphone conpany. Apple the consumer privacy and protection company? I could see it.
If you're looking for an "open ecosystem" option, Mail on both iOS and Mac (as well as a bunch of clients elsewhere, including Outlook and Thunderbird) supports S/MIME encryption and signing out of the box.
Of course, no one uses it or even realizes it's there because S/MIME is terrible.
