THe following was just posted to the Dish Network retailer website.
MPEG II to MPEG IV Upgrades
In order to achieve strategic goals and objectives in 2008/2009, DISH Network will be upgrading the MPEG II (Legacy HD) subscribers to our MPEG IV technology starting the week of 5/18/08. Once upgraded to this state-of-the-art equipment, customers will have the ability to gain access to additional HD content and will be installed with DISH Network's most technologically advanced receivers. Customers will be contacted by DISH Network for an upgrade via various means including auto messages, OTM, postcards and letters.
In the event that you receive customer calls and/or questions related to this upgrade project, please advise your customer to contact the DISH Network customer service center for further assistance.