“It’s true that the Nintendo Switch version is under development at this moment in time,” Okamoto told GameSpot. “Specifically with regards to the development, this game was developed on the Unreal Engine, but the version for Unreal Engine needs to be updated, I suppose, in order to support Switch. In that sense, the development is still expected to take a very long time. It’s still a long ways out.”
Hokuto made clear that the Switch version will definitely be released in the west, and that the while the team considered holding back the PlayStation 4 version to launch simultaneously with the Switch version, it ultimately decided against it.
https://gematsu.com/2018/04/dragon-quest-xi-for-switch-delay-due-to-outdated-unreal-engine-4
EDIT
Square Enix on why Dragon Quest XI was announced for Switch so early
“As we were working on Dragon Quest XI on Unreal Engine 4, we were also wanting to work on the Switch version, as well. Unfortunately, the engine was not compatible at first, though Nintendo and Epic were working on it together. When the engine revision released making porting to the Switch possible, we started working out our plans for the release.”
“We first announced the game before the Switch was even named the Switch, because we wanted fans to know we were working on that version. As the console started to come into focus, we found out that the engine and the console did not work together yet. Throughout development of the game, we worked with Epic and Nintendo to make progress to get the game on the Switch.”
EDIT
Dragon Quest XI for Switch officially based on the PS4 version, won’t be censored in the west
https://nintendoeverything.com/dragon-quest-xi-for-switch-officially-based-on-the-ps4-version-wont-be-censored-in-the-west/
