Yes, I think it is super important that Easel games last forever and that has always been the plan. My long term plan is to create a standalone version of Easel that you can run on your server forever, regardless of what happens to Easel itself.
I'm not yet sure of the details of how an escrow service might work, but honestly, I would be willing to look into it, that could be a good answer. I really do plan on Easel as a platform lasting forever. This is my life's work as much as it is yours.
I believe Github has tools built for leaving a successor in the event of the developers death thats relatively straight forwars.
It seems that Github's successor feature only allows your successor to re-assign ownership for your public repositories. I'm currently using a private repository so this sadly does not work for me. Otherwise I would grab this feature with both hands!
Consider just releasing it under a BSL license forbidding commercial hosting? If that works with your business model.