Sigma is now teasing two lenses for a February 23, 2016 announcement.
The first is the larger “world's first” lens. In the above image, it has been hypothesized that the lens has both a zoom and focus ring in the outline. Which is making a lot of the internet thing it's a faster than f/2.8 short telephoto zoom.
We're told this about the bigger of the two lenses.
The bigger one is indeed a zoom lens, but not a 24-70, not 70-200 and not a 85-135 or a 50-135/50-150
The second in the image above is a smaller prime lens. Sadly, it looks too small to be the 85mm f/1.4 Art series lens. It could be a lens for a mirrorless system(s).
*Note: Most of this information comes from the Sigma Hungary Facebook page, which I cannot find at the moment due to very slow internet access.