The new version of MediaWiki will be on test wikis and MediaWiki.org from 28 September. It will be on non-Wikipedia wikis and some Wikipedias from 29 September. It will be on all wikis from 30 September (calendar).
Latest tech news from the Wikimedia technical community. Please tell other users about these changes. Not all changes will affect you. Translations are available.
A more efficient way of sending changes from Wikidata to Wikimedia wikis that show them has been enabled for the following 10 wikis: mediawiki.org, the Italian, Catalan, Hebrew and Vietnamese Wikipedias, French Wikisource, and English Wikivoygage, Wikibooks, Wiktionary and Wikinews. If you notice anything strange about how changes from Wikidata appear in recent changes or your watchlist on those wikis you can let the developers know.
Changes later this week
The new version of MediaWiki will be on test wikis and MediaWiki.org from 5 October. It will be on non-Wikipedia wikis and some Wikipedias from 6 October. It will be on all wikis from 7 October (calendar).
Some gadgets and bots that use the API to read the AbuseFilter log might break. The hidden property will no longer say an entry is implicit for unsuppressed log entries about suppressed edits. If your bot needs to know this, do a separate revision query. Additionally, the property will have the value false for visible entries; previously, it wasn't included in the response. 
A more efficient way of sending changes from Wikidata to Wikimedia wikis that show them will be enabled for all production wikis. If you notice anything strange about how changes from Wikidata appear in recent changes or your watchlist you can let the developers know.
You can soon get cross-wiki notifications in the iOS Wikipedia app. You can also get notifications as push notifications. More notification updates will follow in later versions.