How receptive would the jenkins community be to replacing the master/slave terminology? Django and drupal have already made such a switch – https://github.com/django/django/pull/2692, https://www.drupal.org/node/2275877 – and I think their reasoning applies to Jenkins as well.
(One could bikeshed indefinitely on replacement terms, and I'm not wedded to manager/worker in any way.)
Changing the code is probably the easier part (though not trivial); there's also lots of documentation that would need to change, not all of it written/maintained by the jenkins project. I think the proejct is worth it even if there is a long tail of references to master/slave references that stick around in docs.