Various online sites are reporting that Apple's iOS operating system version 10 is going to add support for the list unsubscribe header found in many email messages. In case you're wondering, it does sound like this unsubscribe feature supports the "mailto" version of the list unsubscribe functionality. A reddit user posted an example of a generated unsubscribe request here. I'm unclear as to whether or not it will support the "http" version of the list unsubscribe functionality.
The beta version of iOS 10 was released just yesterday, and the full public release is expected to happen sometime this fall.