Problem: Other than the Watchlist which supports live updates, MediaWiki is severely in lacking AJAX-based real-time features, making it rather painful to participate in discussions where new comments are being made in quick succession, among other issues.
Echo alerts and notifications should automatically refresh without a reload/navigation being required – so that users are notified in real-time when discussions they are following have new messages, or when they are pinged. (phab:T34284)
Browser-based push notifications should be implemented for Echo alerts and notifications – so that users are notified even if they just have Wikipedia open in one tab but are working on something else. (phab:T113125 / phab:T276409)
On talk pages, visual indicators like "There are x new comments in this section. Click to reload" could be added (this is currently provided by Convenient Discussions gadget, but could be made more broadly available)
Page history could show an indicator if new edits are made to the page while user is viewing. (phab:T298419)
While viewing the latest diff or permalink of a page, if a new edit is made, there could be a indicator that the content is no longer current. (phab:T295225)
Create an abstraction (such as via polling or EventStreams or WebSockets) that can be used to implement all of the above. It will also empower extension developers to integrate similar features. (phab:T146032?)