The base version of Dragon Quest XI: Echoes of an Elusive Age is no longer available for purchase across digital PlayStation storefronts following this week's release of the special edition. The same goes for the PC version over on Steam, where the listing now states: "This version of DRAGON QUEST XI: Echoes of an Elusive Age - Digital Edition of Light is no longer available. Please see the new DRAGON QUEST XI S: Echoes of an Elusive Age - Definitive Edition." This has happened at the request of the publisher — Square Enix in this case — and so we can assume the situation is the same for the base PS4 version.
A quick search of both the EU PlayStation Store and US counterpart only ever brings up Dragon Quest XI S: Echoes of an Elusive Age and never the original version alongside it. While the special edition does indeed expand on the base game with more content, this is not a Persona 5 Royal situation. Square Enix has essentially upressed the Nintendo Switch port of Dragon Quest XI, meaning its visuals are actually inferior in some places. There's no dramatic difference or anything, but it is one reason why someone may want to purchase the base game over the special edition. That appears to be no longer possible digitally, so a physical copy will be the way to go now. Those who already own the game should still be able to download the original game without issue.