I would be willing to bet it won't be that long. If I were to put $$ on it this will be done in less than 2 yrs. Closer to a 1 1/2 yrs. Space on sats in much more costly than the price of 211's.
Except it is a lot of 622s and 722s to replace 522s and 625s. Not to mention the cost of the service call.
Also, it makes sense for Dish to be incremental. Convert to 8PSK, you can ad a bit more HD. Convert premiums, some more HD space. Convert AT250 channels, and you get more space. Certainly enough to tide most people over. All the meanwhile, customers with 311s, 322s, 522s, and 625s will volunteer to pay money to upgrade to 211s, 222s, and 722s, rather than doing it for free.
I see by the end of the year, non 8PSK receivers like the 301 and 501/508/510 will be gone (the latter are mostly gone already due to Tivo). Probably in the following year, higher tier programming will go MPEG4. But I see 3 years before all programing is MPEG4. Just too many million 311/322/522/625s out there.
Anyway, to the larger point, I wonder if some of this delay isn't due to DirecTV's upcoming launches. No doubt, they want to steal their limelight when they launch a ton of new channels, but D12 is still a week away.