In the school I go to, we had a Dell rep come in today, and because I work with the netadmin for my school, I got to watch the PowerPoint presentation.
I asked him, and he said that the D810 gets a little wider, but a little thiner. They are also sticking with 15.4" Widescreen.
Could tell you a date for release also, but I'm not sure if this information is wanted by Dell to be made available to the general public yet

Lets just say, if it gets released according to the presentation - Ill have one as an EARLY graduation present. (I graduate in the middle of May)