Most if not all of those services were proprietary and tied to the success of one company. Only the Darkmail alliance to the best of my knowledge is actually putting out a new open protocol not tied to their bottom line. Not sure if they have actually put out an RFC yet.
It's like people saying Slack will one day will replace IRC or XMPP. It will never happen. It may if slack started as it's own protocol with a simple RFC and the company was an implementation of said open protocol. Offering a paid option with the option to also do it by yourself for free.
The future of email will start with a new open standard and RFC everybody has access to. It will offer benefits not facilitated by current technologies and will be easily adopted when such happens. Until this happens though there is no reason to replace email. Companies are not going dive into one company and create some massive monopoly who will then hold them hostage.