There are already two fourth Doctor stories confirmed for release in 2010, 1978's Underworld and the 1979/1980 story The Horns of Nimon forming two thirds of the "Myths and Legends" boxset which has been pencilled in for the end of March.
In addition, the DVD extras for a third story cleared through the BBFC today, 1976's The Masque of Mandragora.
00:18:59:04 BIGGER ON THE INSIDE
00:26:22:14 THE SECRET OF THE LABYRINTH
00:07:33:17 THE MASQUE OF MANDRAGORA PHOTO GALLERY
00:09:37:06 BENEATH THE MASQUE OF "THE MASK OF MANDRAGORA"
00:08:38:09 NOW & THEN - THE LOCATIONS OF THE MASQUE OF MADRAGORA
00:02:40:00 DOCTOR WHO (TRAILS & CONTINUITY)