Xbox – Can you pre-order digitally from the Xbox Store

The best answer I can find is this quote from the Microsoft Xbox One Support Site:

Q: Can multiple people share the same console?

A: An unlimited number of people can share the same console.

Note: Your friends and family will only be able to play your games if the sharing feature is enabled.

Source: http://support.xbox.com/en-NZ/xbox-one/games/my-home-xbox

There is also this page regarding playing your Digital Purchases on OTHER Xbox One consoles.

Note: The link to "About sharing games & Gold" is a dead link, but I believe it was meant to point to my previous link.

As retail games are not purchased through the Xbox Live Marketplace, there is no way for Microsoft to know for sure that you are the original owner of the physical copy as physical copies can be sold secondhand. This, however, was possible via Microsoft's original DRM policies when they showcased the One on E3 in 2013. Due to huge outcry from the players for the excessive restrictions of the policies, MS decided to reverse the decision so that discs can now be sold secondhand, which means the 'upgrade' is no longer possible. The 'upgrade', as it was designed pre-2013 E3, consisted of buying a disc and registering it with your Xbox Live account so that it would appear in your list of purchased games.

Sony never offered this option with its PS4 to start with as far as I know. So not much to say here.