In the non Full Frame system we now have mainly two big competitors: Micro Four Thirds and the Fuji X-mount.
It’s interesting to learn that Sigma CEO told this at Dpreview:
“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.“
Good to hear MFT is high on their priority list!