When more HD content becomes available, and perhaps when HD becomes more of the norm for a lot of people in what they will view, in this time of transition, then perhaps the price of HD will drop and that many of those that are SD will be HD instead, that it will just be another version of the channel just as you see the spanish version for some of the channels.
Hopefully Dish will not use this as an excuse to ultimately charge higher prices across the board because of the increase in bandwidth that these channels take up, that the prices each month would get a bit higher for those choosing HD instead of SD, as HD would become more of the norm.
When HD is not considered a premium as it does now and more content is available then perhaps we will see HD channels included. Dish cannot charge extra for HD channels forever if everything eventually is going to be HD.