Java 9 is now officially feature complete, meaning the first bug-fixing phase has started. HTTP/2 Client didn't make it on time for the deadline and has been downgraded to an incubating feature. Since the objective now is to prepare Java 9 for general availability in July, it is very unlikely that any new JEP will be added at this point.
As previously mentioned on InfoQ, the first bug-fixing round, or Rampdown Start, will be aimed at P1-P3 bugs. Among these, and as specified in the process proposed by Mark Reinhold, Chief Architect of the Java Platform, priority should be given to bugs that are new in Java 9, over bugs that affect Java 9 but are already present on Java 8 or earlier, probably under the rationale that the public can more easily tolerate bugs that are already out in the wild than new ones. This idea of focusing on whatever is going to provide a better user experience seems to also manifest in the fact that bugs that refer exclusively to documentation, demos, or tests, are explicitly filtered out from the list of bugs provided by Reinhold; at the moment of writing this article, there were 194 bugs in that list.
This phase also includes a provision for knowingly leaving some P1-P2 bugs unfixed if there is justification for it. Bug owners who wish to defer their resolution must indicate so in the bug report itself indicating the reason for their request (complexity, risk, lack of time, etc.); Area Leads, Group Leads, and the JDK 9 Project Lead will then analyse these data and grant or reject the deferral. At the moment of writing this article, there were no deferral requests yet, although this list may change later on.
This Rampdown Phase comes after an ad-hoc Extended Feature Complete Phase, added to give time to some JEPs to be finished. HTTP/2 Client, together with Enhanced Deprecation, jlink, and the New HotSpot Build System, were features that appeared at risk back in July 2016. Among these, HTTP/2 Client is the only one that hasn't finally made it, turning into an incubator feature. This means that, although HTTP/2 Client will be included in Java 9, it won't be accessible by default: the feature will be packaged under a module with the prefix jdk.incubator., and for that to be accessible developers will have to explicitly use the --add-mod flag. However, if developers choose to do this, they'll need to take into account that incubating features are not part of the standard API, and therefore can be modified at any moment.