If you want to use a 2800 on DISH PRO it is required to use the adapter. When the time comes for you to upgrade ask DISH if they will provide the adapters free they might just to keep customers. If not see if they will give a deal on DP-301s?
Next year a DishPro+44 switch will be available (although unknown whether it will come with the SuperDish but will be made for it) in which will have the legacy/DP adapter built in it. That means you would not have to purchase an adapter for each legacy receiver to have it work with DishPro lnbfs and DishPro switches.