What a thoughtful question! I am sure your employers will appreciate anything you can do to ease their transition. Once you get that next job, you should make sure to let your employers know (hopefully with advanced notice) about your needing to move. Generally, their biggest concerns are how to handle the transition from one person to the next. Maybe you can map out a plan for how you can continue to work until the next person is up and running. This would mean letting them know with enough advanced notice so that they can hire someone new (maybe you can help to recommend people or interview folks), and help to train the new person. You are not required to do any of these things, but they do show that you value the firm and are trying to ease their concerns about the transition. Good luck!