Your "in place forever" conflicts with the comment to which I have asked for an explanation what the new rules are:
callahad:
"5. We have a new channel, which new rules." (sic)
Note that the Developer Edition is definitely new (1), and callahad also explains in his reply where it is positioned:
"As far as fundamental web platform features are concerned, the Developer Edition is a normal pre-Beta channel. It's primarily that more willing to promote new tooling up from Nightly into the DevEdition or to set different default preferences, for instance."
1) https://hacks.mozilla.org/2014/11/mozilla-introduces-the-fir...