Recently the IETF working group on HTTP met in Berlin, Germany and discussed the concept of mandatory to offer TLS for HTTP/2, offered by Mark Nottingham. The current approach to transport security means only 1/5 of web transactions are given the protections of TLS. Currently all of the choices are made by the content owner via the scheme of the url in the markup.
It is time that the Internet infrastructure simply gave users a secure by default transport environment - that doesn't seem like a radical statement to me. From FireSheep to the Google Sniff-Wifi-While-You-Map Car to PRISM there is ample evidence to suggest that secure transports are just necessary table stakes in today's Internet.
This movement in the IETF working group is welcome news and I'm going to do everything I can to help iron out the corner cases and build a robust solution.
My point of view for Firefox has always been that we would only implement HTTP/2 over TLS. That means https:// but it has been my hope to find a way to use it for http:// schemes on servers that supported it too. This is just transport level security - for web level security the different schemes still represent different origins. If cleartext needed to be used it would be done with HTTP/1 and someday in the distant future HTTP/1 would be put out to pasture. This roughly matches Google Chrome's public stance on the issue.
Mandatory to offer does not ban the practice of cleartext - if the client did not want TLS a compliant cleartext channel could be established. This might be appropriate inside a data center for instance - but Firefox would be unlikely to do so.
This approach also does not ban intermediaries completely. https:// uris of course remain end to end and can only be tunneled (as is the case in HTTP/1), but http:// uris could be proxied via appropriately configured clients by having the HTTP/2 stream terminated on the proxy. It would prevent "transparent proxies" which are fundamentally man in the middle attacks anyhow.
Comments over here: https://plus.google.com/100166083286297802191/posts/XVwhcvTyh1R