We know that Alcon Entertainment and Warner Bros. are working  with Ridley Scott to make another film  set in the Blade Runner world, though whether the new film might be sequel, prequel or spin-off we haven't known. Hell, we really don't know anything about the movie, including the key question: "why?" (Answer to that is likely to be "because we can.")
Now Ridley Scott says that the Blade Runner project is "likely to be a sequel."
That quote above is reported by the Wall Street Journal , to which Scott also said,
I think I?m close to finding a writer that might be able to help me deliver. We?re quite a long way in, actually.
So... no script yet. I don't know what "we're quite a long way in" means, given that there isn't even a writer hired, but that's why he's Ridley Scott and I'm not.
That means that this could end up not being the next film that Scott makes after his Alien prequel Prometheus. Last time  we heard anything from Andrew Kosove from Alcon, he said that this film wasn't likely to go into production before 2013, meaning this is probably a 2014 release at the earliest.
And while I'm dubious about this project, I was also concerned about the idea of an Alien prequel, and Prometheus has turned out to be a lot more promising that I would have guessed at the outset. It still might not be a good movie in the end, but Scott and his many conspirators have swayed me there, so it could happen again with Blade Runner.
Oh, and with respect to Harrison Ford's character Rick Deckard, are we likely to see him in the new film? "No, not really," says Scott.