Hopefully it will hit all four big carriers. HTC nearly pulled that off with the 8X if Sprint wasn't hemming and hawing about WP8.
There is an advantage with HTC and LG coming in the fold (and we know LG has a phone on the horizon as a new one is showing up in ad tracking) in that both of them have very good carrier relations in the US. Nokia did not, so carrier whims mattered more.
Big question will be the length of the Verizon window. If AT&T is already saying they are getting it, my guess would be Verizon will have the exclusive through the end of September. I know there's a big NFL campaign planned by Microsoft and Verizon to highlight the One for Windows. It may just be planned for the first month.