As Cimi said, graphical changes to the UI are likely to introduce more visual noise/clutter and make things less clear (and in the case of slow connections or devices, reduce utility).
Michi's suggestion ("...enforce that an existing item cannot change physical location when a new item arrives") would give a far more stable/ predictable user experience and is, in my opinion, the way to go.
As Cimi said, graphical changes to the UI are likely to introduce more visual noise/clutter and make things less clear (and in the case of slow connections or devices, reduce utility).
Michi's suggestion ("...enforce that an existing item cannot change physical location when a new item arrives") would give a far more stable/ predictable user experience and is, in my opinion, the way to go.