The Road to Firefox 57 has been updated with a couple of changes to the timeline:

Firefox won’t run in multiprocess mode unless all enabled add-ons have the multiprocessCompatible flag set to true or are WebExtensions. This means that developers who haven’t set this flag don’t have to worry about multiprocess compatibility and can focus on WebExtensions and the Firefox 57 deadline.

The multiprocess compatibility shims will be removed earlier, starting with the Nightly and Developer Edition channels. Their purpose was to ease the transition to multiprocess compatibility, but given the change in the previous point, they aren’t really needed anymore. Removing them will help track performance issues.

None of these changes should require any immediate action from developers, but let us know if you have any questions or concerns.