I come to you today with (possibly) solemn news. This won't be a large post.
It looks like the movie is on hold. And has been. For two years. The official release date is still early 2016, though that is now impossible unless the film is to be released without any marketing (much like the fourth game was). Late 2016 might still be possible to hit, though if I were a betting man, I would say early 2017 or later. Remember, Ratchet got delayed from 2015 to 2016.
I'm really just compiling information here, so take this as you will. These next quotes are pulled from Twitter.
XdernexCuba: @kevmunroe Sly Cooper The Movie. how long be finished :(
kevmunroe: @XdernexCuba we have to start it before we finish it :) Just waiting on the green light to do so...
― January 1st (source)
@kevmunroe (obviously) is Kevin Munroe, the director/writer of the movie.
TheIronicTea: @IanJames007 Are you still working on the upcoming Sly Cooper movie?
IanJames007: Haven't heard a peep.
― January 7th(source)
@IanJames007 (again, obviously) is Ian James Corlett, the voice of Sly Cooper.
Now, this can all mean a variety of things, but it sure sounds to me like they are waiting for the Ratchet & Clank movie to come out before they even get the green light to work on the Sly Cooper movie.
Here is the link to that tweet by Ian James Corlett, but it seems like the tweet by Kevin Munroe has been removed, or at least, I can't find it.
A few acknowledgements before I wrap this up; the tweet by Kevin Munroe is visible in this video by VtnVivi, and the tweet by Ian James Corlett was pointed out on the Sly Cooper subreddit by TheIronicTea themself, here.
One more thing, this is the first in (hopefully) a series of News blog posts related to the Sly Cooper film. We have a portal for the film, which can be viewed here and easily accessed by clicking "Film Series" on the navigation bar at the top of the page (if you're on desktop, of course).
Fingers crossed,
Teenbat,
bureaucrat for the Sly Cooper Wiki