I am interested in knowing Atlassian's position on Java updates w/ regard to Oracle's new release model:

10.x is Java's latest release - but this now changes every six months!

For full details, please see:  http://www.oracle.com/technetwork/java/javase/eol-135779.html

This is my summary of information gathered from the link directly above:

General Availability (GA) for Release 8 was Mar 2014 with its end of public updates for commercial use after January 2019 and non-Corporate desktop use after December 2020.
 
GA for Release 9 was Sep 2017 with its end of public updates on Mar 2018 (why you do not see 9 anymore for Java downloads)
Java SE Downloads Site:
http://www.oracle.com/technetwork/java/javase/downloads/index.html

GA for Release 10 (18.3 or YY.M) Mar 2018 with its end of public updates Sep 2018

GA for Release 11 (18.9 or YY.M) is scheduled for Sep 2018 with its end of public updates TBA

My recommendation:

Knowing all this now, support for Java 9 should not be considered and developer work should stop on that - if it has not already.  Jira support requests should be created based on the new release model.  I think Atlassian should definitely focus on Release 11 as support for Java 8 may be over after January 2019.