Update 2: The game's Japanese website has confirmed that PS4 owners won't be able to upgrade to Dragon Quest XI S. The title is also a port of the Nintendo Switch version. You can read more about all of that through this link.
Update: There's no mention of any free update for existing Dragon Quest XI players in the official press release for Dragon Quest XI S on PS4. Even the in-depth look at what the expanded game brings to the table on the PlayStation Blog doesn't touch on the subject.
It's looking like this will be a full price re-release, folks.
Original Story: Dragon Quest XI S: Echoes of an Elusive Age -- which is an expanded and improved version of Dragon Quest XI -- is coming to PlayStation 4 later this year. This definitive edition originally debuted on Nintendo Switch in September 2019, and now it's finally heading to Sony's system as well. It'll release on the 4th December, 2020.
The only problem is that we don't know whether existing players will have to buy the game all over again. Hopefully all of the new content and improvements are made available as an update, but again, we don't have any confirmation yet. We'll update this story as soon as we know more.