The answer isn't satisfying, but it isn't shocking either. The BBC has no plans for any more adventure games. They've been set aside for games that are not part of the BBC license fee, such as Doctor Who: The Eternity Clock and the MMORPG Doctor Who: Worlds in Time.
So, unfortunately, even though series two was announced to be "bigger" than series one, it's actually one quarter smaller. At least we can hold solace in the fact that The Gunpowder Plot, the only episode of series two, is much better than any of the games in series one.