How will this affect current domain squatters? Will they be required to follow this when they renew these domains? Or is this just for new registrations moving forward?
It doesn't, aside from it being more difficult for them to hide behind invalid contact details, which should make it easier for others to initiate UDRP proceedings against them.
As soon as they register a new domain with a registrar under the 2013 RAA or if they update their contact details, they'll be forced to validate them.