Interstellar has been in development for a number of years, growing from a first draft developed by Steven Spielberg and CalTech scientist Kip Thorne. Somewhere along the line Jonathan Nolan came on to do some drafts.
A couple of years ago Spielberg slipped away from the film and since then, I really wasn't expecting that we'd ever see it.
But I guess Nolan liked what he had done, and told his big brother all about it as, according to The Hollywood Reporter, Christopher Nolan is now negotiating a deal to both produce and direct the film.
The basic idea for the film came from Spielberg's "amateur interest in astrophysics." He found about wormholes and wanted them to become the centrepiece of a story. Kip Thorne layered on some time travel and parallel universe ideas. It was all super-vogueish science… a few years ago. It's settled in a little more, now.
So that's some of the backdrop to Interstellar, but we don't know anything about what the actual story is. There's really not much to go on here, just the confusion that the title refers to things happening between stars but the premise is apparently about things happening across far wider gulfs of the continuum. Makes me think that the film is about an attempt at interstellar travel that's then disturbed by the unexpected discovery of a wormhole. We'll see.
UPDATE: Kip Thorne gave away the basic details of the plot, at least as it was, in 2007. The Australian spoke to him then reported:
The plot of Professor Thorne's space adventure revolves around explorers who travel into another dimension through a wormhole, a hypothetical short-cut shaped by something called warped time-space.
Explorers plural and the setting is a different dimension. That's worth knowing, just about.
Interestingly, Thorne considers wormholes to be just theoretical. Asked if they exist he said "Probably not."