Since, patch for exposing current wait event information in PGPROC was committed, it becomes possible to collect wait event statistics using sampling. Despite I'm not fan of this approach, it is still useful and definitely better than nothing.
In PostgresPro, we actually already had it. Now, it's too late to include something new to 9.6. This is why I've rework it and publish at github as an extension for 9.6: https://github.com/postgrespro/pg_wait_sampling/
Hopefully, it could be considered as contrib for 9.7.
------ Alexander Korotkov Postgres Professional: http://www.postgrespro.com The Russian Postgres Company