The film industry is a crazy, wonderful, unpredictable circus at the best of times, where the most unlikely projects are completed before you even knew they were going ahead (Jeepers Creepers 3, anyone?), and viable sure things somehow end up unable to escape from development hell.
These 13 films have each been in some stage of pre-production for quite some time, be it months, years or even decades, and despite the insistence of those involved, it's simply hard to believe they're ever actually going to make it to cinema screens worldwide.
Either because of the overly ambitious scope of the project, the excess of cooks in the kitchen, scheduling issues or a combination of all of the above, these films will require too much time, effort, money and sheer mental energy to actually get before cameras.
If these predictions are wrong, then fantastic, but given the fickle nature of film production and how easily projects get quietly canned, you're best off not holding your breath for these long-awaited films...