With no fourth installment coming (unless “The Hobbit” prequel is made), the DVD for The Lord of the Rings: Return of the King will be released sooner than expected. May 25th is the date set for the release of the double disc edition, as opposed to the usual August release dates.
Details about the DVD is sketchy at the moment, although just like the final Matrix installment, it is likely to be jam packed with extra features. The Extended/Collector's editions will be released nearer to Christmas.
This article in the Beeb and other news sources suggests that a "20 minute theatrical trailer" will be present on the initial release.