As Kotaku points out, Nintendo currently ships its first-party Switch games with downloads ranging between 2 and 6 GB, though third-party developers have been releasing "bigger, data-heavy games, outpacing the Switch’s 24 GB of usable onboard memory."
Nintendo's new 64 GB cards were originally slated to come out in the second half of 2018. According to the Wall Street Journal report, they will now begin coming out sometime in 2019. No specific release date or window was given.
We've reached out to Nintendo to confirm this report and will update the story should we hear back.
Since its release back in March 2017, the Nintendo Switch has sold more than 10 million units, making it a large success for the company. According to another report by the Wall Street Journal, the company is planning to sell upwards of 30 million total units next year.