DirecTV & HDTV Question

I plan on buying a DirecTV oval dish with 3 LNB's & receivers for the
present. I was told by Circuit City that when I want to convert to HDTV that
it will require use of 2 of the LNB's just for HDTV. I will also need an
HDTV receiver. Is this true about the current technology about the use of 2
of the LNB's? I checked with DishTV and they even require a separate dish
for HDTV. Are there  any upcoming changes to the DirecTV for HDTV?