I think we have plenty of out of focus short films already, shot on 5D full frame cameras.
IMO APS-C/Super 35 is the sweet spot, east to get shallow DOF shots and easy to keep things in focus.
Even though full frame cameras can be used with amazing results, most people abuse them, and it gets quite hard to shoot wide open with a full frame camera.
16mm sized sensor is great for documentary or one man shoots, as it's much easier to keep things in focus, and yet it can also look cinematic.
It's definitely a useful format that should be supported by modern cameras.
There's also loads of high quality 16mm glass available, calling it a hipster trend is shortsighted to say the least. :)