If you want the world’s fastest lens for any digital mirrorless system than grab the Handevision 40mm f/0.85. You can preorder it now in four different mounts at BHphoto:
Handevision IBELUX 40mm f/0.85 Lens for Canon EF-M Mount (Click here)
Handevision IBELUX 40mm f/0.85 Lens for Sony E Mount (Click here)
Handevision IBELUX 40mm f/0.85 Lens for Micro Four Thirds Mount (Click here)
Handevision IBELUX 40mm f/0.85 Lens for Fujifilm X Mount (Click here)