One of the main points why Amazon moved to Leipzig/Germany in the first place is, that it is only 25km / 15 miles to the next airport. This airport is also one of three global DHL hubs and the only global DHL hub in Europe. I would suspect they don't want to give up this position.
I'm waiting for the day Amazon takes out the logistics middlemen and has it's own long-distance delivery fleets (trucks and planes). I think it is inevitable at the scale they operate under. If/when that happens, it will be interesting to see where the locate their warehouses.
I don't know. Right now they commoditize delivery (the customer doesn't pick who delivers the package, just the delivery terms) so they can take advantage of the best rates for any individual package. It will be hard to compete with that internally.
