No, not at this time, the 7s is only for local feeds, but only time will tell, they may end up using it for HD feeds, if it gets delayed much longer. But, you may see network HD feeds going on it, but you can only get them if you are in an O&O market or get a waiver. However, they are epected to "double" their HD lineup by years end, but at this pace, I don't see it happening.
DIRECTV has a ton of locals on national beams. With the addition of D-7s they will be able to move these to spot beams. They will then have more national beams available for things like less compression, more HDTV, and new channels.
There is no mandate to broadcast in HD. You are confusing it with SD digital. all broadcast's must be in at least SD digital by the end of 2006, with no analog broadcasts of any kind. That date will most likely change. I don't see everything being broadcast in HD for a very, very long time.