Dragon Quest XI is set to release in July on PlayStation 4 and Nintendo 3DS in Japan. Meanwhile, the date for the confirmed Switch version has not been verified. Square-Enix assures its development, but a launch window remains unknown.
Famitsu reveals that Dragon Quest XI may not appear on the Switch until 2018. In their most recent publication, they changed the launch date from "2017" to "To Be Announced".
This is obviously just a rumor, but Famitsu has been quite reliable with Square-Enix news in the past. The change could very well be significant. Square-Enix however, assures that Dragon Quest XI is still coming to the Switch, regardless of any changes in release dates.