Earlier quoted context omitted.
Archive team seems like the appropriate end for these accounts. Maintaining accounts for deceased people for the remainder of the lifespan of the internet is not really a sustainable thing.
maintaining accounts for deceased people for the remainder of the lifespan of Twitter is probably sustainable, though.
Also, Twitter may disagree with you on its lifespan. I wouldn't, but I do believe that unless they do start archiving, it will reduce its lifespan, perhaps considerably.