Personally, I think this is 1-2 years out, as they are still a while from moving the content off 110/119. It is likely that the LNB will be redesigned to handle the D12 satellite at 101, and then 110/119 would only be needed in markets with SD locals for SD only customers, or perhaps for internationals.
This would allow a slightly smaller dish for standard HD installs.
I predict mid-to-late 2009 for a general release, although we may see the dish in testing before that.
These are just my predicitions based on what I have read, nothing from Directv here.
Even if they speed up the transition by moving the older HD channels to the new D11 satellite and speed up swapping customers over to new equipment, there is still no need for the new dish until D12 is up in the sky and done testing.
DirecTV has shown, however, that they will start installing dishes as much as a year before thes sat is launched, i.e. the AT9 dish used before D10 was launced, even in makets without locals on the Spaceways.
Again, just an educated predicition