Hello there, @KrisBumsted ...
Interesting question. I'm not sure if I have an answer for you, but you could certainly test this out on your own since you have admin rights to your Canvas environment. When you say that an instructor leaves, are you also deleting that person's account from your school's Canvas environment completely?
You could either use your school's Canvas "production" environment (the environment you always sign into) or your school's Canvas "test" environment (a separate environment where you can play around with things and not disturb anything in the "production" environment).
In either case, you could create a "sandbox" course and then create a "dummy" account. Then, once the "dummy" account has been created, enroll that user in your "sandbox" course with the "Teacher" role. Sign in as the "dummy" account, and then add a video to the Studio library via the "Studio" global navigation button on the left-hand side of Canvas. Log in to the "sandbox" course, and embed the Studio video. Then, sign out of the "dummy" role. Log in with your own account, and completely delete the "dummy" account you created. Then, still logged in as you, go into that "sandbox" course to see if they embedded video still exists and is playable for you and students.
I hope I've understood your question correctly. If not, please let me know. Hope this helps, though. Take care...be well.