tldr: we are going to do a first merge of m-c => m-b and use the
devedition population one week earlier to push 57.0b1 & 57.0b2.
In order to maximize beta testing, we are going to take advantage of the
fact that we have a different set of users with the developer edition
(which is, since the completion of the dawn project, based on mozilla-beta).
September 14th, we will merge mozilla-central => mozilla-beta and
mozilla-beta => mozilla-release. September 19th, we will push to the
devedition population the first beta of 57. Later, we will be pushing a
second beta to this channel.
In parallel, to minimize the impact on the developer, mozilla-central
will remain 57.0a1 and will be merged to mozilla-beta transparently.
Nightly will become 58.0a1 on September 21th.
The regular beta population will remain on 56 and will be provided
updates to the RC builds.
The milestones are detailed in this Google doc:
In parallel, as the soft freeze demonstrated its value during previous
cycles, we are going to use this again during the 57 nightly cycle. From
September 18th, we will ask you to land only bug fixes, stability or
important performance fixes. New development not planned for 57 should
land once mozilla-central will become 58 (September 21th).