During the Asus Eee PC announcements in Germany and Austria last week the German Asus press representative Holger Schmidt made a statement to a press agency called pressetext that the Asus 8G would come with a larger 10 inch display.
The dimensions of the Asus 8G with a 10 inch display would stay the same. The Asus Eee PC measures 225x165x35mm (8.8x6.49x1.37inch). A 10 inch screen can fit easily in there. The maximum diagonal is 10.9inch.
If this turns out to be true, I am even more motivated to wait until the Asus Eee 8G becomes available. I have already considered getting an Asus Eee 4G upgraded to 1GB RAM.
The specifications published by Asus initially state a 7 inch display for the 8G also.
More details on Der Standard (Austrian). Via Eee-PC (German).