Billie returns as Rose Smith?

Lifetheuniverseandcombom has posted a article about the possibility of Rose and the other Doctor returning, now as Mr and Mrs Smith!
Just found out this morning that Tennant is coming up to London on Friday to shoot a scene with Billie Piper. And it is literally just the one scene. Episode 4.18, Scene 163 to be precise. They’re going to be out on location in a reasonably public place so there’s some chance of photos but I don’t want to be too specific in case the descent of hordes of ‘Doctor Who’ fans prompts anyone to try and find out where the information originated. No idea what the scene actually entails but the Call Sheet lists the characters as “The Other Doctor” and “Rose Smith” so draw your own conclusions!
Please take this as a rumour until images are released or the BBC confirm it!