All we have to go on is an image showing the latest revision. The track pads are still in but it seems Valve have decided to scrap the traditional d-pad for a thumb stick.
If you have been following the development of this controller you would know that Valve had decided to avoid the traditional dual thumb sticks found on every other modern controller in favour of touch based track pads. This was originally to help bridge the gap between games that would be best played with a keyboard and mouse and provide some better support for them on a controller.
It's possible that the thumb stick is used to make the controller even more versatile and usable in a larger range of games.
Will this be the final design of the controller? It's hard to say until the controller has been released.
What do you think about this? Will the controller be revolutionary or will it bring nothing new to the table?