Though Nokia has reiterated they wouldn't be tampering (at least not heavily) with the UI, and we have seen that they haven't with the current Lumia devices.
S.Elop did say we would see some proprietary changes to the windows phone UI when Windows Phone 8 is released later this year, but just how much change are we going to see? no one knows yet.
The guys at pocketnow came across a few of the proposed UI (a concept UI) made by the guys from Nokia's R&D team and from the looks of this, it is a total overhaul of the windows metro UI. So this is not going to make its way to WP7 platform, I would rather see this on Symbian IMHO.
It would be really cool if this or something close to this is used to bring Symbian back!
For full story and more pics see HERE