It will suck to have to resort to essentially MITM tactics on my developer workstation in order to decrypt local traffic. Yes, there are tools like Fiddler that can do this, but eventually it may be impossible to MITM traffic the way Fiddler does. That will make it more difficult to debug applications. There are also platforms like Pivotal Cloud Foundry that rely on being able to inject headers into HTTP messages as the messages traverse the platform (e.g., to support throttling); this will become more difficult if that traffic has to be encrypted.
HTTP/2 with forced TLS is, in effect, a binary protocol. Right now, developers all over the world enjoy the plain-text and hackable nature of HTTP 1.x.