Despite the bankruptcy of AlphaDream, it seems Nintendo is bringing Mario & Luigi series to the switch or Smartphones. As Letsgodigital shares, on January 9 Nintendo of America presented a registered trademark in Argentina for Mario & Luigi. Here is the description of Trademark
Nintendo Mario & Luigi trademark description: Computer game cartridges; game memory cards; computer game software; video game memory cards; interactive entertainment software to play video games; covers for mobile phones.
In light of the above document, It seems Nintendo is working on this project. For now, We can’t say they are bringing back the same series or working on a completely new series.