WAYYYY too many people are making the assumption that Dish would be better off airing the new channels in MPEG2 for starters, then move them to MPEG4.
That would be a patently ridiculous strategy for Dish to take. (Sorry it appears I'm picking on you, KenSoren; I just chose to use your quote 'cuz you write really well.)
Look at the blowback Dish is taking right now: they have some new channels, but you need new hardware to see them. But your old hardware works just fine for the stuff you have been receiving, and will into the forseeable future.
Compare that to what has been proposed on these and other boards: Here's your new channels, enjoy! Until we TAKE THEM AWAY FROM YOU. You'll have to pay money to view the same programming you had been viewing, up until now.
(And don't confuse a 3-day preview, like Showtime occasionally has, with making a channel available for months on end. Viewers would get used to it being there and would have conniptions even if they're constantly told it was a preview.)
See what I'm saying? It's all about deciding for yourself whether you want to spend the money to upgrade.
The alternative is to let Dish decide whenever they want to shake you down for more money (for new hardware) in order to see channels you already get. I think nobody will want that precedent established, even Dish.