You can already preorder the new A7III at Amazon US, Wex UK and at Calumet Germany

UPDATE: Preorders now up on all stores:

Sony A7III in USA at Adorama (with free overnight shipment), BHphoto, Amazon,  BestBuy, FocusCamera.
Sony a7III in Europe at Calumet Germany, ParkCameras UK, WexUK.

And join our Sony A7III Facebook group!