I was looking at hmv and came across this:

Star Wars Trilogy 4DVD Special Packaging

Also the 2004 DVD's are appartently deleted (see see here)

The 2004 DVD's were dispointing, the 2005 DVd's were pointless, the 2006 DVD's were a joke and it seems the 2007 DVD's are a tired old joke you've been told you too many times.

I'm betting that they are rereleasing them in these "slimline" dvd cases that seem to be popular for releasing box sets now, just so the transport costs are less (as the boxes are half the size) and they can make more profit. Still there's alway a chance we may see some nice cover art for the original trilogy

edit:
it seems amazon also have it up for preorder here, release date 12 Nov 2007.