It could change, but the video was pretty clear: October for the 350, November for the 750.
That was UK availability, but I would hope once the factory is spitting them out they'll ship them everywhere...
One thing to be careful of: it's possible that JVC hasn't set the price. They could be reading these forums to try to judge the excitement before setting the price. Every glowing positive "I've got to have one" comment here adds $100 to the eventual price, so please stop being excited. Find little nitpicky things to complain about instead.
I've got to have one! (ca-ching!)