verizon only?
For one to three months, it seems. Google has a history of this, giving a US carrier a brief exclusive before making it available to multiple carriers.
All speculation at this point, of course, but I'm putting it at 75% certain that Verizon will have it for the month of November by itself, 50% certain for December as well.
T-Mobile in January and maybe at&t too. Sprint sometime in the spring...