While I'm not sure if it will work with newest communication (winbeat 6.x -> ELS parser -> ELS database), I am sure that I can support you in making it work.
There's no official statement that parser's plugin will not work with winlogbeat 6.x, so that's good.
Assuming it won't work I have one workaround from the top of my head: worst case, we can use combination of two agents winlogbeat and filebeat. https://www.elastic.co/guide/en/beats/winlogbeat/6.8/configuring-output.html
But first, let me know if it beat in 6.x worked!
