Short answer: No.
Long answer: Not really.
Longer answer: The new design of the Galaxy S6 makes it much more difficult to change the back panel / battery cover. Instead of the traditional plastic removable panel, Samsung have instead opted for a glass back, which is only intended to be removed by service professionals. It is technically possible to do given the correct tools, and you can even get a replacement battery here, but this is not the quick battery swap that was possible with earlier models.
However, Samsung have tried to ensure that replacing the back cover isn’t as necessary as it once was. The battery charges faster, and is now capable of getting 4 hours more life in just 10 minutes of charging. The phone also lasts longer, thanks to a more efficient display and processor. Wireless charging is also included, making it more convenient to charge your Galaxy S6, and there are ways to extend your S6 battery life too.
Very astute!
Considering its not even out yet I don’t think you can change cover as you haven’t got one