According to rumors originating from the website Windows 8 Italia, Windows 8 will have two different interfaces - one for the 32-bit version and the other for 64-bit version. The new interface which will be available with the 64-bit version is said to be codenamed "Wind".
According to the rumor, the system requirements for running Wind is quite high and it will be available available only in high-end systems with dedicated video cards. It is also said to be fully 3D capable - although will also work on a non-3D monitor. Wind is also said to be completely dynamic - the shortcuts and the interface are said to be able to adapt according to the user's usage pattern and different scenarios which may arise.
32-bit systems and 64-bit systems which cannot run Wind will have the second interface which will not have any of these features.
Windows 8 is also said to have a new fast hibernation system which takes only 3-6 seconds. It is also said to have a new intelligent SSD management which will improve the performance while increasing the longevity of the SSD.
As of now, all of these are mere rumors as there is no way to confirm any of them. So take them with a pinch of salt.
According to previous leaks from Microsoft, we are two years away from knowing if any of these are true.