At Photokina 2018 press event, Sigma announced that they will also make L-mount lenses for Panaosonic Lumix S1 & S1R full frame mirrorless cameras. And they will also make EF to L mount and SA to L mount Len adapters for Panasonic FF mirrorless cameras.
Here is the detail from Sigma press event:
- Sigma FF Foveon L-mount mirrorless camera coming in 2019
- SA-L and EF-L lens mount adapters to be released in 2019
- First Sigma L-mount lenses will be released in 2019.
- L-mount conversion service will start in 2019.
You can find more info here.