According to recently rumors from SonyRumor.co, Sigma will announce their first full frame E-mount lens in 2017. Sigma CEO already said that they are planning to make Sigma FE lens for Sony full frame mirrorless cameras at Photokina 2016.
The first Sigma FE lens will be a prime lens, will be much cheaper than currently Sony/Zeiss FE lens verison.
via: SonyRumors.co