From SciFi Pulse:

Changes are ahead for both Doctor Who & Torchwood.First off on Torchwood things are going to change massively. Leaving the show are Burn Gorman [Owen Harper], Naoko Mori [Toshiko] and John Barrowman [Captain Jack Harkness], though it is likely that Barrowman will return now and then as Captain Jack in a recurring capacity.Joining the team as a full time member as of season 3 will be Freema Agyeman who will step in as Martha Jones and take over the day to day running of Torchwood from Captain Jack. Remaining with the show will be Eve Myles as Gwen Cooper.Another big change for Torchwood is the format of the show. Up until now the series has been aimed at a more grown up audience, and has been sold as a Science Fiction series for adults. This has allowed it plenty of latitude with regards to sexual innuendos and humour. Some of the humour may stay, but it will be dumbed down somewhat so as not to alienate the younger audience members.A third season of Torchwood has indeed been commissioned, but thus far only for five episodes as apposed to the usual 13. Which is something, that has many in the industry somewhat puzzled, especially considering that the show is performing better than Doctor Who in the USA.The above changes to Torchwoods format are so it can be shown in the Saturday evening slot that is usually occupied by Doctor Who. Producers at the BBC are looking to Torchwood to act as a buffer between seasons of Doctor Who.So when Doctor Who isn’t on the air. Torchwood will be there to fill that void in time and space that fans have when waiting an entire six months for the DR. Who Christmas special.While on the subject of Doctor Who there is a good reason why Catherine Tate is leaving after the one season. Much like Martha it was planned from the start. Though the big difference is Donna whom Tate plays in the series will turn out to be a pretty nasty piece of work. Which is why we have a series 4 finale that will include the return of Captain Jack, Sarah Jane Smith, Martha Jones and Rose Tyler.In addition to this my source has informed me that David Tennant will be leaving the series and will regenerate during the last few minutes of the 2009 Christmas Special.Apparently for the last few months filming has been underway on the four Doctor Who specials. The first of which will be the 2008 Christmas Special followed by two specials in the year and ending with the 2009 Christmas special which is in its final six weeks of production now. Tennant will officially have left the series in two weeks time when he finishes filming the final moments of the 2009 Christmas Special.

Tipped to take over from Tennant is Full Monty Actor Robert Carlyle though. One insider at the BBC claims that negotiations are currently underway with the actor.Although the above has come from a pretty reliable source. I ask that you treat the above as you would any other rumour until such times as the BBC actually make some kind of official statement about both series.

I myself are hoping all these to be rumors and none to be true!!! David Tennant has to stay longer as the Doctor!!! Think of how many fans he will be letting down!!!