We’ve been told that a 24mm f/2.8 DN Art lens for Sony’s APS-C E-mount platform was in development at Sigma, and planned for release in September 2015. The Micro Four Thirds mount was not mentioned.
In January 2013, Sigma announced a set of DN optics for MFT and Sony E-mount. This lens family has not seen any new member since then.
Sigma has yet to venture into large aperture territory with its mirrorless lens designs. A 24mm f/2.8 DN would surely be a nice addition though, especially if performance is high across the field wide open.
This rumor comes from a new source, so take it with the usual pinch of salt!