Leo and I attended the Paris OSGeo Code Sprint at Mozilla Foundation put together by Oslandia and funded by several companies. It was a great event.
There was quite a bit of PostGIS related hacking that happened by many new faces. We have detailed at BostonGIS: OSGeo Code Sprint 2016 highlights some of the more specific PostGIS hacking highlights. Giuseppe Broccolo of 2nd Quadrant already mentioned BRIN for PostGIS: my story at the Code Sprint 2016 in Paris.