As of the information from Eldar Murtazin it seems that Windows Phone 9 & Windows RT is going to get new UI. The Windows Phone 8 is having a new User Interface which is called as the “Metro” which is having so many tiles so the navigation is going to get changed. Eldar Murtazin once said that Microsoft is going to buy Nokia, so as it was true now, this rumor also must be true.
Lets us wait to see whether Microsoft is going to change the UI of the Windows Phone 9 and the Windows RT ie Tablets UI. The Metro UI what we are using now is good only for the touch based interfaces and somehow people are looking for more alternative since it was almost occupying all the home screen. So if the UI was change in Windows Phone 9 then it was better welcomed.