As such if Amazon develops their own shipping, FedEx and UPS will not suffer for it that much.
$12bil in shipping is quite the market to lose. This isn't UPS/FedEx losing the home portion of the shipping which they may barely break even, this is them losing it all. Amazon is rolling out planes, has their own trucks/trailers, and now outsources with an Uber like delivery system. No matter how you cut it, that's a huge client to lose, especially since the volume of Amazon was so great they had to use UPS/OverNite/FedEx/DHL/USPS just to maintain demand.