Menu's don't really need a touch interface. That'd be a lot of investment for very little gain over leaving the touch pad out and just using menu's and D-pad navigation.
IMO the main purpose of the touch pad ought to be expansive, immediate interfacing. You can have virtual buttons with a broad enough placement that it's obvious to the user. Better yet, it should have positional continuity with the game, such as selecting an area in an RTS to calling up tactics. Broad positioning on touch pad can be married to AI target selection, so a pass can be made in a football game based on the smartest choice in the touched vicinity, versus the timed press and the like of current games. I suppose for menus there could be something like four drop-down tops on the top of the screen, with a corresponding touch on the top of the pad in the equivalent column bringing down a menu which you can slide down to make a selection. That'd be quick. I don't suppose it's accurate enough for inventory management in a Wii U like way - that'd need a screen.
If all touch adds is a gimmicky interface, swiping instead of pressing a button, it'll contribute nothing of value to the future IMO
How big is that touch pad going to be? I suppose that if it's large enough they could stencil in some outlines for zones on the touch surface, so it could be used like buttons if you wanted, with clearly defined button areas.
To me, it would make for an incredibly poor twitch area, because it's in the center of the controller. Lots of games have controls for switching weapons, picking up and dropping things, inventory and menu screens, or even buttons to bring up OS functionality. That leaches a lot of buttons you could use for twitch things like movement, attacks, reload etc. If they can make that surface free up physical buttons for better things, I'm all for it.