Xbox One GamerScore Achievements will be transferable from the Xbox 360 to the new system. However Xbox Live Arcade games that you’ve purchased on the Xbox 360 will apparently NOT transfer over. The reason is due to the wildly difference and complexity in the new system’s architecture compared to the old.
However either way you slice it this is a HUGE blow. And may prevent people from purchasing anything digital AT ALL in the future. I could see this becoming a huge problem later down the road for the game industry at large.
– Thanks to Willie’s World of Wallpapers for the image.