Steven Moffat told SFX in its newest issue that Rani will not be making a return to new who, the reason "...No one knows who the Rani is.." That was his response to the question of if he wants Rani to make a return.
Moffat continued to say "They all know who the Master is, they know Daleks, they probably know who Davros is, but they don't know who the Rani is, so there's no point in bringing her back. If there's a line it's probably somewhere there."
He followed up with the fact that bringing back old villains can be effective for Doctor Who, but said he doesn't want to overly rely on the past.
"Even people who don't know the past very well get thrilled by the idea that you've brought something back," he explained. "Everyone got very excited - and by everyone I mean real people - when the Master came back, even though most people could barely remember him."
Moffat concluded saying "It has to be self-explanatory, it has to be free-standing, it has to be clear for everybody. If I did the Meddling Monk teaming up with Mavic Chen's daughter and the Krotons then yeah, that's too much, because no one gives a toss." (By the way I think this would be amazing!)
I just hope they will bring back the Ice Warriors.