The premise for Interstellar was pretty well-guarded when it was a Steven Spielberg project; now that Christopher Nolan has come onboard, and the script has mutated somewhat, all clues as to what it's actually about have retreated even further into the shadows.
There are going to be wormholes, I think. Possibly time travel. Possibly parallel universes. Maybe there's no difference between those two things. There could be a lot of speculative fantasy in this film, masquerading as science.
Mysterious, in any case. But we're at least finding out who's going to be in it.
Of course, that's all they know. She'll probably be in the film. As something.