Great, what happens to all that back history when it's "shut down"
As one of the cadre of people who never agreed to use Facebook, I still want them drawn and quartered for enabling facial tagging in photos w/o the consent of the people being tagged. Yes way back at the beginning that's how it worked. They also would spam your email address if one of your friends made the mistake of ever logging into the app on a device with your contact info on it. And of course the only way to opt out was to permanently create a Facebook account and then log in constantly to discover what privacy settings they changed and what new hell they had opted you into. And even more spam.
How much you want to bet the plan to "shutdown" Facial Recognition won't involve disclosing who they tagged(including non-facebook users), what third parties accessed or used the information, or let those people (users or not) review that data, or delete it after the inevitable storm of lawsuits that are coming.