At the moment, we don’t even know if it would be possible for her to make a return appearance after her travels with the Doctor. “Wibbly-wobbly, timey-wimey” may well make it impossible for him to ever see her or Rory again. Although there is always that fan who’ll think “well, you say that now…”
In the past, even the closing of a breach between two parallel universes wasn’t enough to prevent the return of Billie Piper as Rose Tyler (2008) while Martha Jones (Freema Agyeman) turned up in Doctor Who episodes that year as well as Torchwood Series 2 some months earlier.
She also revealed that she’s been in contact with the actress who plays the Doctor’s latest companion, Jenna-Louise Coleman. And what does she do with this contact? She tells her things about Matt Smith, of course.
Obviously, opinions are divided on whether her permanent absence is a good thing or not. Some will be sad to see her go, some will be glad of it, and some can think of other characters that they would prefer to leave. What do you guys think?