The Nintendo Switch will soon receive three more Dragon Quest titles in Japan, as the original Dragon Quest, Dragon Quest II: Luminaries of the Legendary Line, and Dragon Quest III: Seeds of Salvation will be released on the same day as Dragon Quest XI S: Echoes of an Elusive Age - Definitive Edition.
The Dragon Quest series is a huge deal in Japan, to the point where it's practically a national treasure. Square Enix has gone out of its way to port as many of the games in the series as possible to mobile phones, as the turn-based nature of the series lends itself well to a touchscreen. The mobile ports of the Dragon Quest series are excellent and they can easily form the backbone of ports to other systems.
The Nintendo Switch is about to receive three more Dragon Quest titles, as ports of the original trilogy will be coming to the system on September 27th. According to Gematsu, the games will cost 600 yen, 850 yen, and 1500 yen, respectively. The reason for this escalating price is due to the size and scope of each of the games, as the original Dragon Quest is quite easy and short, while the third title expanded the setting a great deal.
It's possible to play all of the mainline Dragon Quest games on Nintendo systems, but they are spread across different consoles. It's clear that Square Enix is making a push to bring the Dragon Quest series to mainstream popularity in the west, which is likely why so many protagonists of the series became playable in the Hero character in Super Smash Bros. Ultimate. It's possible that all of the mobile ports of the series will come to the Nintendo Switch in the future, including the localized versions that are already available. The chances of these games being available on the Nintendo Switch outside of Japan will likely depend on the reception to Dragon Quest XI S: Echoes of an Elusive Age - Definitive Edition.
Dragon Quest, Dragon Quest II: Luminaries of the Legendary Line, and Dragon Quest III: Seeds of Salvation will be released for the Nintendo Switch in Japan on September 27, 2019.