We have told Sigma will announced another full frame lens sometime in 2013. This rumored lens is Sigma 24-105mm f/4 DG OS HSM lens(Not sure if has optical image stabilizer).
This lens might be a good replacement for the EF 24-105mm f/4L IS USM and AF-S NIKKOR 24-120mm f/4G ED VR lens.
See also: List of Sigma Lenses to be announced before Photokina 2014.