At the start of October 2019, the developers behind Mario & Luigi: Bowser's Inside Story + Bowser Jr.'s Journey had to opt-out of game development due to poor sales. Since then, the Mario & Luigi series has taken a bit of a back seat until now.
According to a new trademark filed by Nintendo America found by LetsGoDigital, the Mario & Luigi series might not necessarily be completely dead. The new trademark has been filed in Argentina for new Mario & Luigi "Computer game cartridges; game memory cards; computer game software; video game memory cards; interactive entertainment software to play video games; covers for mobile phones."
It should be noted that this trademark covers "mobile phones", which could mean that the next Mario & Luigi game (if there is one being developed) could be a mobile-based game that isn't arriving on the Nintendo Switch. Hopefully, Nintendo does bring back the series as its been going since the Game Boy Advance generation back in 2003. If Nintendo is making a new Mario & Luigi game, would you like to see it on the Nintendo Switch or mobile? In my personal opinion, I'd prefer it on the Nintendo Switch if it's still going to play like the original games.