UPDATED: Estimated arrival date released. In a stunning development, Sigma has placed the rumored 24-105mm on their website. I say stunning, because the whole of the Sigma USA team is on holiday today and we were never briefed on this lens officially (which is HIGHLY unusual, eg. this is the first time it's happened). This story is still developing, but the page is live and you can look at it yourself.
UPDATED: Sigma expects the lens to be available by November.
"True to its categorization as a Sigma Art lens, the new 24-105mm F4 DG OS HSM is designed for artistic expression and top-notch image quality. This versatile lens covers the basic shooting range from wide to medium tele with an inner focusing system that eliminates front lens rotation, enhancing the lens stability and allowing the use of circular polarizing filters. It also boasts a constant aperture of F4, and contains Sigma’s proprietary Optical Stabilizer (OS) technology to compensate for camera shake. Moreover, it was designed to surpass the required quality inspection of every Global Vision lens with Sigma’s own modulation transfer function (MTF) “A1” measuring system to create new optical standard to align with the high-spec cameras on today’s market."
Lens Construction: 19 elements in 14 groups
Minimum aperture: F22
Filter size: ø82mm
Angle of view (35mm format): 84.1°-23.3°
Minimum focusing distance: 45cm/17.7in.
Dimensions (Diameter x Length): ø88.6mm x 109.4mm/3.5in. x 4.3in.
Number of diaphragm blades: 9 (Rounded diaphragm)
Maximum magnification ratio: 1:4.6
I grabbed some great product photos of the lens for you to gander at as well:
No price has yet been listed, and all my sources have not been able to get me one. I'll update as soon as I hear.
View the full product description, MTF charts, and all other info at Sigma-global.com.