Version 4.11.0 of #syslog_ng was released yesterday. I submitted changes to the #FreeBSD ports maintainer, but if you are impatient, you can already try this syslog-ng version from my test repo:
The main new feature is a #Kafka source.

Installing a syslog-ng 4 development snapshot on FreeBSD
Unless there is a <a href="/community/b/blog/posts/installing-syslog-ng-4-0-1-on-freebsd">serious problem</a>, FreeBSD ports usually contains the latest stable syslog-ng release. However, sometimes people want to compile a git snapshot to test a new feature or bugfix. To do that, one way is to <a href="/community/b/blog/posts/compiling-syslog-ng-git-snapshots-on-freebsd">generate a syslog-ng release tg...</a>