Series might not be done - latest podcast interview on Pajama Pants -
https://youtu.be/E8A8YV1yRBA
Sounds like whatever project he wanted to move on after Mr Inbetween just isn't working for him and on a few occasions throughout the interview talks about the possibility of a 4th season or film which he really left the door open with not killing Freddie. And really I think deep down he misses the character. Fx would be crazy not to fund a 4th series or movie - prefer 4th season.