User blog comment:Merrystar/Adopting a wikia/@comment-26037236-20150618082106/@comment--20150620075606

I don't know about being "worried". Generally as an expected courtesy, older admins will respect new ones that come into play. It is totally your decision as the new active admin of your Wiki to decide if you would like the inactive admins/bureaucrats to be demoted in the Wiki you adopted.

Bureaucrats cannot demote other bureaucrats (and if you adopted a Wiki, you should have those rights). Only Staff can demote bureaucrats. As far as "undoing your edits" that shouldn't be a problem unless the user is very stubborn, and not willing to work with others. Depending on how long they've been inactive for, they may not come back, but if you really are that worried you can think about sending a request to demote :)