Third party lens companies afriad of E-Mount?

With the high success and sales rate of the NEX system, you would think more third party lens companies would be willing to make some E-Mount glass. With the limited glass selections from Sony, and the couple lenses by Sigma still leave a huge gap to be filled. I would think that other companies would see opportunity here to make some of their own glass for E-Mount. Do you think other lens companies are afraid to adopt the E-Mount?

Or another idea I had was that other companies want to make some NEX glass, but Sony is only giving the rights to very specific companies to make E-Mount lenses for fear of having a plethora of inferior glass flooding the market giving the NEX system a bad name?