According to ABC's Medianet website, the American network premiere of Harry Potter and the Goblet of Fire will be on Saturday, April 26, 2008.

When Harry Potter and the Sorcerer's Stone and Harry Potter and the Chamber of Secrets were premiered on ABC in May 2004 and May 2005, respectively, previews for Prisoner of Azkaban and Goblet of Fire - which had not been released at the time of the first two movies' television premieres - were aired with the respective showings.

There is a possibility that previews for Half-Blood Prince will air during the telecast for Goblet of Fire next month, though this is not confirmed.

We will update when we have more information about the telecast.

UPDATE: Warner Bros. has stated that there are no current plans to premiere any footage from Half-Blood Prince during the Goblet of Fire telecast.

Thanks to Michaela for the tip!