I see my 722k as a timeless gem. It took what was already a groundbreaking HD DVR (622/722) and made it even better. It and the Hopper are the reasons I stick with Dish.
As far as compatibility is concerned, the 622/722 series are on par with Hopper. As long as the Hopper is the current gen, the ViPs will be right there with it. Hopper just took what the ViP started and made it even better. Just like the ViP did the same with the 522/625. So what if Dish doesn't make any more, if what you have works, then there is no need to be concerned. Only those with truly obsolete receivers need worry.