You keep going on about a change in usability.
You're easily younger than I am. Please do not attempt to talk down to me.
As long as you don't go insane with thematic elements, no, it does not. Design your icons (and dock background) to look how you wish and change those.
A complete interface change would require developers to update their app icons to match, and I can't see people changing 50,000 apps just because Apple wants them to look different.
I think the home screen could use a little bit of organization, but the OS as a WHOLE "looks" old. I think the pixels could be changed without the need for moving the UI around or confusing people.
By the way... I've always hated how the Clock, Weather and Photos icons look. So far, the Calculator, iTunes Store, Stocks, SMS, Phone, and iPod icons have changed... why not others?