We spoke with a few Nvidia partners and they said that Nvidia wants to sell the console itself. We learned that the general opinion is that giving the console to partners such as Asus, EVGA or Lenovo would make the partners fighting each other for their space under the sun, something that might potentially hurt the product.
Nvidia will take care of the distribution and sales just as it did with 3D Vision glasses that can be purchased in usual retail and etail stores. The same thing should happen with the Shield console when it is ready to launch.
From what we learned it might be a few months at least before we see the Shield console in retail.