The BBC is reporting that both David Tennant (the 10th Doctor) and Billie Piper (Rose Tyler) are confirmed to continue their roles in the "third series" in 2007. This would dispel any rumours of Billie Piper leaving after the 2006 series.
It is also revealed == Minor Spoiler Alert == that Rose kisses the Doctor in the upcoming 2006 series. "...Although all is not quite as it seems," reports the BBC news article.
It continues, "Without wanting to give away the plot, it must be said that Rose is not responsible for the lip-smacking action."
Also mentioned in the article is that Russell T Davies would like to pull in more guest actors/actresses to the series even from Hollywood. On the top of his list is Sigourney Weaver, known to most science fiction fans for her role in Alien and Ghostbusters.
Davies also admits he would not have a problem with the Doctor regenerating into a woman. Though this is not an issue at the moment since David Tennant is eager to stay in the role for now.
Read the complete article here: BBC News - Third series for Dr Who and Rose.