For the classic series: 16th April will be the delayed classic series story Survival; 28th May will see the release of Tom Baker's premiere, Robot; and 25th June will be the Colin Baker story Timelash.
For the new series, 2nd April will see the release of last year's Christmas Special, The Runaway Bride - in a change to last year's release form, the DVD will just consist of the special (ie. without Smith and Jones). The first 3rd season release is to be expected in June.
With the exception of Survival, extras for the forthcoming releases are yet to be revealed, though Tom Baker mentioned in the recent New Beginnings boxed set that he had recorded a commentary for Robot.