According to leaked image its is being said that, Microsoft will bring a slightly changes on its UI design, Windows Defender, One Drive and with the Windows activation process. With these changes Microsoft can also major update as introduce the Cortana in Windows 9 version.
At the mean time it is not been cleared at the hardware requirements for the Windows 9 as last time Windows 8 makes the hardware to update. Right now it's not known whether the Windows Phone 9 will support the current high-end WP devices. Earlier, Microsoft had rolled out Windows Phone 8 with new devices, while none of then WP 7 devices were updated to the new version.