First draft of PREMIS 3 ontology was released January 2017 so nothing is final yet but this is an initial review of what would change should Phydo update to using PREMIS 3.
File Set and Work Property Changes
There aren't many PREMIS properties being used for File Set or Work properties but there are a few. The first and second tabs of the spreadsheet (File Set Properties and Work Properties) recommend mapping these to other properties that are not PREMIS at all.
Events are a bit different under the PREMIS 3 ontology. The third tab of the spreadsheet (Events) shows recommendations for mapping all events we are interested in tracking in Phydo.
PREMIS 3 events serialized as Turtle files (for easier reading):