I don't believe they have any lease options for a 721, but I know you can purchase one, if there are any in their warehouses. I'd call Dish and ask about the lease, wouldn't hurt.
If you have been a customer for a year or more there might be some other dvr deals. I spoke to a csr last night and she said wait till December as they have some special upgrades coming. They wouldn't give me any more details. I'm not expecting anything so we will see.