Buying Sigma DSLR camera and lenses - A smart Investment?

I am still in the progress of having hard decisions whether to buy the Sigma SD15 or a different DSLR camera. After reading some comments from photographers on the Sigma forums on dpreview, I have noticed that many photographers are concerned about the future of Sigma in the DSLR market. Every photographer knows that Sigma is a large and popular interchangeable lens manufacturer, but in the DSLR