Although, this could be worked around by downstream projects by specifying a feature set, so unlike the FFmpeg 4.x woes here, the -sys problem isn't a showstopper.
EDIT: Maybe not, I misread the patches.ffmpeg-sys is a pretty straightforward bindgen crate and it’s not really FFmpeg 4.x aware. Not sure why you think -sys is the issue.My fork hasn’t been updated to support FFmpeg 4.1 yet. (I’ll get to that soon.)