This has been widely circulated on the internet, including Doctor Who News Page:
A decision has been made by DVD production company 2Entertain to release the eleventh Doctor's adventures without the "Next Time" trailers, as (not) seen on the recently released Volume One; this impacts both the DVD and Bluray formats.
According to emails sent to Radio Free Skaro and reported on their twitter account, the decision was made "at executive level" in 2009.
Another difference to the original broadcast has been specified as: "a slight change to the sound effects used on the transmitted version. Lightning sound effects were added, particularly as Matt and Karen’s names appear, just prior to TX that only the TX version would have." This change is expected to be corrected for the Boxed Set version due out later in the year.