Speaking about this issue, the developers confirmed that the Xbox One and PlayStation 4 cannot import save files from previous Witcher games, though they can ‘simulate world states.’ This is, of course, best experienced on PC, where there are no compatibility issues, but on the consoles, it becomes trickier- the Xbox One and PS4 are both incompatible with their predecessors, which makes the issue of save data from the older games a bit complicated, not to mention that PlayStation has never even had a Witcher game before this one (and Xbox never got the first Witcher game).
One of the ways in which CD Projekt RED’s The Witcher series is notable to its Bioware siblings is in how the developers strive to create a persistent, continuous thread throughout the games, so that it feels like one story from start to finish.