The dSLR market is a tough one. Canon and Nikon have the largest part of the money pie here with very large catalogs of cameras aimed at all possible customers (from $600 to more than $5000). Sony arrived later to grab its own share and seems to be succeeding thanks to its Minolta heritage (it is said that they already got more than 15% of the market).
Other brands are fighting to keep in sync with the rate of innovation. I would list here Pentax (and its Samsung partner), Panasonic and Olympus, Sigma, etc. These companies have obviously smaller research and development budget for their SLR camera ranges. And this is a tough issue for them.
Recently, at the opening of the Photokina, Sigma announced a new camera, the Sigma SD15. What I think is impressive is the fact that -in the midst of a storm of news- Sigma could only provide a sketch of the features (essentially, this will be a 15MP camera using the new Foveon X3 sensor, with attached high-quality expectations).
I feel that this is significant of the difficulties to keep the pace. Sigma needed to provide some/any information about new products to avoid appearing absent for the market, but where is the real product. I fear this is going to be tougher and tougher for them, not even counting the fact that they are developping their own sensor (a nice differentiating move aiming at the hghest image quality, but a real drain of resources).
Will Sigma be the next big SLR photo manufacturer to drop it?