Those are the latest Sigma rumors: next week Sigma will announce a new 17-70mm lens with OS (optical stabilizer). The current model sells for around $369, expect the new model to be more expensive.
Next year Sigma is expected to announce a new 70-200mm lens (also with OS) with very high quality glass (probably f/2.8).
The last lens from Sigma was the 70-300mm f/4-5.6 DG OS (announced on September 4th, 2009).