TL;DR: When active app development resumes, this will be a top priority, but there's really no timeline for when that will happen.
Unfortunately, even for an app like ours which supports a wide variety of screen sizes and configurations, updating to the iPhone X will be a major undertaking. Not only do every screen edge hugging elements (e.g., the draft indicator) need to be revisited but every screen needs to be tested in portrait and landscape. I've estimated bare-bones support for X as a 2 month project, but given current product priorities that's no target start-date for the project.
The good news is there's really no path forward with iOS development that doesn't involve supporting the X, so when development resumes it'll need to be the top priority.