From what I have read, Kizumonogatari is a prequel for Bakemonogatari, and the movie is reported to be scheduled for fall 2013.
However, Monogatari Series: Second Season was just released this summer (2013), and is still ongoing, so I thought this movie might not be released (again) this fall.
Have they delayed it again?
On October 4, 2015, Shaft announced that Kizumonogatari will be released - not as a single film, but as a 3-film series: Tekketsu, Nekketsu, and Reiketsu. These are the three adjectives that Koyomi uses to describe Kiss-Shot, meaning "iron and blood" (as in Bismarck), "hot-blooded" (emotional, impassioned), and "cold-blooded" (cold, calculating), respectively.
The first movie, Tekketsu, premieres on January 8, 2016. There's a new PV out for it, distinct from the old PV from back in 2011. Premiere dates for the second and third parts are as yet unknown.
There is actually a list of theaters in Japan that will be airing Tekketsu, so I think we can rest assured that this is not an elaborate Shaftian trolling effort.
At the time Tekketsu was announced, no information about outside-Japan airings of the film was made available. However, Aniplex, which is the producer for the Monogatari series, has been fairly good about securing outside-Japan airings for its past films, most notably the three Madoka movies. So there is hope.
This answer is outdated. See Senshins answer.
There is currently no release date for Kizumonogatari. It was listed for Fall 2013, but was removed, so there's no official release date yet.
Source: ANN - Kizumonogatari Film Briefly Listed for Fall (dated 2013-07-31)
