One of the key arguments when Mozilla decided to implement EME was that the crappy-proprietary-code could be sandboxed by firefox to ensure that it doesn't infect a system with malware, spy on users, etc.
From a security perspective it's light years better than flash and other crappy plugins.
Today that has low impact, in a few years that situation will be untenable for FF and they will be "forced" to cave once again in order to appease users that do not care about privacy or security
Don't forget that vendors like Netflix aren't proponents of DRM, it complicates their streaming architecture and costs a lot of money.
In a future where Netflix and other streaming services makes up a large part of the profit for content owners, we might see DRM disappearing.
Look at how Apple was able to sell DRM free music because their volume was high.