"Those games will continue to run on your Xbox 360 for as long as your Xbox 360 runs," Microsoft Game Studios VP Phil Spencer told GameSpot. "The box is not backward compatible and we think for somebody who invests in a large digital library that you want to keep your [Xbox 360]. Keep that as a vibrant part of the ecosystem."
Continuing to play on an Xbox 360 while others are on Xbox One won't be an alienating experience, Spencer said, because friends lists and achievements will remain constant between both platforms.
Read more of "XBLA games won't carry over to Xbox One" at GameSpot.