According to Emily Rogers, a Nintendo journalist and reputable leaker, Mother 3 is still planned for release in North America. Rogers believes that there will be more news on the title at this year’s E3.
— Emily Rogers (@ArcadeGirl64) April 29, 2016
For reference, Emily Rogers correctly predicted a new Paper Mario for Wii U and the fact that Zelda was in development for the Nintendo NX.
We will keep you updated on any new information on Mother 3 as it becomes available.