Who'd have though that the first vendor to build in support for ES6 modules was going to be Microsoft?
Of course it will be at least 10 years before people can safely require Edge and another 5 years before that version of Edge current enough to support modules.
Remember: IE11 will be supported with Windows 8, 8.1 and 10 until at least 2020 and the enterprise version of Windows 10 never gets feature updates and thus never an updated Edge.