My experience is that Hive is pretty widely used, I have a lot fewer data points about Pig. We're not particularly attached to either of these. That sentence was more to indicate that we'd be adding some sort of interfaces for specific data types.
Seems like we got our history wrong here. When was YARN added we'll add a correction.
Hope this helps clear things up.
Note that YARN also supports Docker containers as of Hadoop 2.6...
YARN-1964: Create Docker analog of the LinuxContainerExecutor in YARN
I'll stick with http://www.dbms2.com/2014/04/30/spark-on-fire/ however, for the most part. (The mid-2014 PR blitz I thought I was engineering didn't actually happen.)