PostgreSQL 9.6beta1 came out yesterday. It is the first version of PostgreSQL that will have parallel query support and PostGIS 2.3 will be the first PostGIS to support parallelism in queries. Although work is not yet committed in PostGIS repo to support this, you can expect to see this soon (currently here - https://github.com/pramsey/postgis/tree/parallel , waiting for someone to you know who you are do something about it.)
Because of the newness of the parallelization feature, there are some caveats. As with all big things, we expect there to be a lot of bugs, and the more eyeballs on those and real workloads we've got hammering on them, the sweeter the PostGIS 2.3.0 and PostgreSQL 9.6 release will be.
Binaries for Windows users
For windows users, winnie the PostGIS windows buildbot is now building PostGIS for 9.6. Get PostgreSQL 9.6 binaries and installers from PostgreSQL 9.6beta1 for windows.
Once you have that, just copy the contents of the respective PostGIS 2.3 9.6 binaries listed here - http://postgis.net/windows_downloads/ into your install folder.
In the extras folder, you'll also find ogr_fdw foreign data wrapper latest development version which we covered extensively in FOSS4GNA2016 PostGIS Spatial Tricks. Talk also covered some new PostGIS 2.3.0 stuff.
We don't have pgRouting binaries available yet. pgRouting team is working out some compatibility issues with PostgreSQL 9.6. Once those are resolved, we will publish pgRouting binaries as well.