The one major advantage to TLS everywhere will definitely be avoiding mixed-content issues when eg you have a web forum and someone tries to embed an image on a non-TLS server into their post. Hopefully IE's choice to be the one non-TLS HTTP/2 supporter doesn't undermine this.
Since this is just going to be how it is, I just hope we can do more to make setting up TLS easier for everyone.
Ah, once again Microsoft is the one that supports less security than the other major companies. Microsoft needs to distance itself a bit more from law enforcement agencies.
I got the impression that Microsoft is backing this because of pressure from large enterprises, which do not want to deploy TLS in their intranets. I don't believe IE will prefer plaintext HTTP/2 to TLS HTTP/2, and it will certainly deploy both.
Put another way: I don't believe Microsoft is worse than Google in this regard.
Opportunistic Encryption is still on the table as well.