It's not the HD part- it's the MPEG-4 part. They will eventually shift completely or nearly so to MPEG-4 from MPEG-2. That takes the new receivers. The shift will let them get a lot more programming out with the same bandwidth. That translates into money in the bank. And since more programming will be available in HD, they'll need that bandwidth, and as it becomes more popular, they will save money by having the option of just upgrading your programming package to include some HD package, just like you upgrade from AT60 to AT120 today. Otherwise, they'd have to send out a new receiver, all too often.
No, it's pretty clear both satcos will move to all MPEG-4 & HD capable STBs as soon as possible. Those that don't want the HD function won't subscribe to it. The only reason for limiting ViP STBs to HD subscribers today is to restrict it to those that actually need it- and that policy will only last as long as it's in short supply.
A move to digital is mandated by law. A move to HD is not. We'll never see 90% of channels in HD in our lifetimes.
"...They will have to start leasing those 622s without requiring a subscription to the HD pack ($20/mo.) at some point. ..."
Yes, of course.
"...We shouldn't have to pay an extra $20/mo for channels we don't want just to have the current flagship DVR...."
Then why would you want the "flagship" DVR? Currently, that's the only reason for getting that DVR. Later, when it's in greater supply, it'll become the only DVR, unless they come out with a fancier model, and they won't require the metallic pack subscription. It'll just have the ability to receive certain programming (HD) that you may not subscribe to. Kinda like today.