I don't think we will see them push the 721 heavily untill Internet access is available for the unit.
They kind of pushed it to the market for those who "must have" the unit now.
Once the 721 has all the bells and whistles it is supposed to have they we can expect Echostar to push the 721.
As of now, you can't buy a 721 from Dish Network, you have to get it from a retailer.
BTW the 721 IS indeed Dish Network / DirecTV compatable, I understand for it to see the DirecTV data stream a software update must first be sent to the unit, then it will be able to see both services.
I do believe that they mentioned this in a few articles as well as on the chats.