Good news for Rose Tyler fans: Billie Piper is back on Doctor Who for a three episode stint in now-filming season 4, according to BBC News and the official Who web site.
The Doctor Who news site Outpost Gallifrey originally reported the news, after forum members photographed Piper on set at the production's studios in Cardiff, Wales. A statement from the Who office would say only that Piper was indeed back on the show. "Anything you may read elsewhere about when, how or for how long Rose returns to Doctor Who should be treated as pure speculation at this point," the statement warned.
This news means that David Tennant's Tenth Doctor will have a superfluity of companions in season 4. In addition to season-long assistant Donna Noble (Catherine Tate), the former "runaway bride," it has already been announced that last year's assistant Martha Jones (Freema Agyeman), who switched over to Torchwood, will rejoin the Doctor partway through season 4 in time for his meeting up with the revamped Sontarans.