Here's my understanding of the chronology so far:
1.  Filed by @jdforrester-wmf in 2012-06-24
   * Title: "//VisualEditor: Parsoid needs to hint on each 'internal' link as to the status of its target (redlink; stub; interwiki)//" 
   * Description: "//For the arbitrary stub threshold preference, perhaps just hint with the character length of the link and leave it to the UI to decide how to render based on user preferences? This would mean that we wouldn't fragment the parser cache...//"
   * Assignee: @GWicke
2.  @Gwicke drops priority to lowest priority on 2012-06-29
3.  Jan 2013: new title "Implement rendering of redlinks and stubs" (moved out of #Parsoid and into Bugzilla's "General" project) T39902#413848
2.  Discussion in 2013, suggesting Action API changes, and hinting that "bug 11" (T2011) could be fixed by this
3.  Feb 2014: James reports that @Catrope will attempt to implement this, "at least as a first run" and raises to high priority (T39902#413952).
4.  March 2014: James fixes related issue T39901
4.  Early 2015: James drops Roan as assignee, @ssastry drops priority to normal
8. Sept 2015: @Jdlrobson expands the task description (T39902#1690785)
1.  March 2016: @gwicke flags this as an #ArchCom-RFC
8. April 2016:
   * #ArchCom very briefly discusses this in E161 as part of our planning/triage
   * @gwicke posts an implementation strategy, but remarks "As far as I am aware, there is currently no API that lets us efficiently retrieve the list of red links in the current version of a given article." (T39902#2208376)  
   * @anomie responds, advising about how to do this, but cautions: "//We might have to disable it (or reduce the functionality) in miser mode though, like we do with various other parameters, to avoid bugs like T97797.//" (T39902#2209625)
   * @gwicke ties this to the change propagation service (T133221) and suggests Parsoid would need to provide redlink markup as part of the re-render request (T114413). (T39902#2240375)
9. August 2016: @Jdlrobson cross posts "[Redlinks in Android app](https://lists.wikimedia.org/pipermail/wikitech-l/2016-August/086242.html)" on mobile-l and wikitech-l: "//I've cced wikitech in case anyone has an update.//"  

Next steps?  I suppose #ArchCom can discuss this in E258, and possibly make this a candidate for one of our office hours in the not-to-distant future.  We can discuss the #ArchCom-RFC triage process in Z425.