As you have seen, there's a WIP PR to implement removal of Java 7 support: https://github.com/apache/spark/pull/16871
I have heard several +1s at https://issues.apache.org/jira/browse/SPARK-19493 but am asking for concerns too, now that there's a concrete change to review. If this goes in for 2.2 it can be followed by more extensive update of the Java code to take advantage of Java 8; this is more or less the baseline change. We also just removed Hadoop 2.5 support. I know there was talk about removing Python 2.6. I have no opinion on that myself, but, might be time to revive that conversation too.
