Sigma CEO Yamaki spilled out some beans in an interview posted by Dpreview:
Sigma plans to launch a couple of properly designed mirrorless L-mount lenses in 2019. I believe those lenses will be available for Sony E-mount too.
Yamaki said this: “Fujifilm doesn’t really disclose the protocol between the lens and camera, so we need to do the reverse engineering by ourselves.
It’s a really time-consuming process so we need to prioritize support for Sony E mount, our L-mount system, existing DSLR mounts and Micro Four Thirds.”
New f/2.0 primes:
Sigma is considering to launch smaller and more compact f/2.0 primes for mirrorless cameras