Consent must be asked for in a clear understandable fashion.
Burrying some legalese crap at page 29 of your 12'000 word TOS doesn't cut it.
Could be that Facebook tries to push the envelope yet again. They may come to regret it.
If I had to bet, it will not be the case that we'll see some big exile of users as a result of having to click through an additional "Agree and Continue" dialogue to get to what they were going to do anyway. The GDPR will do a lot more to appear to be doing things right than actually benefiting users.
/snark
You have a right to learn what data they have about you, with whom they share it and a lot more details In addition you can opt out of anything you agreed on earlier and I would be surprised if you can't request deletion if the business has no business reason to store it. (Arguably, a difficult call with Facebook whom's entire raison d'être is to fuck with your privacy).