If you read between the lines a bit, it's clear that what they want is encryption to/from cloud hubs where data is stored using escrowed keys (a.k.a. server-side "encryption"). Many services already more or less do this, so the goal would be to push the entire market in this direction and then eventually to outlaw or otherwise restrict systems that do not work in this way.
This fits in with the dumb terminal / mainframe model of the Internet being pushed to varying degrees by most of the tech giants these days and with Amazon's vision for IoT.
It's stupid and naive to claim that there is some technical barrier to what the FBI wants. It's actually quite easy if we apply a bit of government pressure to push the Internet even further toward the "put everything in the cloud" direction it's already going. Anything in the cloud is almost by definition backdoored.