When Mario Kart Tour was first announced last year, it was slated for release on Android and iOS sometime before March 2019. Now, in Japan, the smartphone game has been pushed back to summer.
Nintendo of America has yet to announce whether or not the U.S. release has also been delayed. This article will be updated if that announcement is made
スマートフォン向けアプリ『マリオカート ツアー』は、アプリの品質向上および配信後のサービス内容拡充のため、配信予定を2019年夏とさせていただきます。 pic.twitter.com/YhtI2DWw4H
— 任天堂株式会社 (@Nintendo) January 31, 2019
The reasons Nintendo game for the delay was to “improve quality” and “expand the post-release service content.”