Although I haven't seen an official announcement by Sigma just yet, a 24-105mm f/4 DG OS HSM "Art" lens is already featured on Sigma's website.
Lens Specifications:
Lens Construction | 19 elements in 14 groups |
Minimum aperture | F/22 |
Filter size | 82mm |
Angle of view (35mm equivalent) | 84.1°-23.3° |
Minimum focusing distance | 45cm / 17.7in |
Dimensions (Diameter x Length) | 88.6mm x 109.4mm / 3.5in x 4.3in |
Number of diaphragm blades | 9 (rounded diaphragm) |
Maximum magnification ratio | 1:4.6 |
Weight | 885g / 31.2oz |
Update: It looks like Sigma removed the webpage from their server. However, an official announcement is surely not far off.