The MediaWiki community generally does a good job of noting important architectural changes in release notes so users can stay updated by reading them when updating to the next release. For developers who work with the master branch there isn't any convenient way of learning about them as soon as they happen, though.

It would be nice if release note changes could be announced as soon as they are merged (or proposed in a changeset, even?) to increase developer awareness. This is not really worth spending human time on but it doesn't seem too hard to have an IRC bot parse commits / new changesets and make the announcements.