The commercial arm of the BBC have made the decision in order to focus on other Doctor Who gaming projects including the upcoming console game The Eternity Clock.
Executive producer Steven Harris gave a statement to Digital Spy:
"Right now there are no current plans to develop any more Adventure Games, so [The Eternity Clock] is the next Doctor Who gaming exercise and we're doing other things."
"Obviously we've got the browser-based MMO Doctor Who: Worlds In Time, we have other plans for other platforms and formats and we'll be announcing those."
"But right now The Adventure Games have done a great job, and they've been done, we're now going to move forward with the The Eternity Clock and we'll continue to develop those plans as we go ahead."
"The Adventure Games are actually done by the production team down in Cardiff, and there's a question about now BBC Worldwide is focusing and investing in these developments, that providing audience expansion and providing something that's going to hopefully broaden the Doctor Who audience."
"That's something we're going to pick up on in gaming for the foreseeable future, and the team down in Cardiff are going to concentrate on some other things - which I've seen some of their ideas they haven't announced yet - but there is going to be some cool things around that to continue developing what they do around public service, around audience expansion for the UK licence payers."
Doctor Who: The Adventure Games were launched in 2010 and have been huge success with over 2.6 million downloads to date.
(Source: Digital Spy, with thanks to the TARDIS Newsroom)