Now available for pre order at Amazon, listing an
October 2 release date.
I ordered 4. 
And a reminder once again: we still don’t know whether the new Hue motion sensors will be visible to SmartThings or not. It could end up being a parallel means of control, like the Hue dimmer switch or the Hue tap.
That is, SmartThings would know if a bulb attached to the bridge came on that had been triggered by the motion sensor, but it wouldn’t know anything about the motion sensor itself.
That will still work for my purposes, but it’s just not yet clear whether the Hue motion sensors could be used to trigger other SmartThings events. We’ll just have to wait-and-see.