For some reason Leica did show the R7 on display at Photokina as the model for the R10 but I don't think they will keep the shape. Rather the size and build quality. So one shouldn't take it so serious.
I would think the size of Canon 5D or less, based on the size of the S2, and the design towards the S2 which is anyways a redesign based on R8/R9.
See the video on my R10 site which I think gives a good idea about the thinking behind it all:
leica.overgaard.dk - Thorsten Overgaard's Leica Pages - Leica R10 Full Frame 35mm integrated dSLR camera coming in 2009-2010