Speculation is starting to run rampant that Nintendo is developing a mini Game Boy that will essentially act like a Game Boy with built-in games much like the NES and SNES Classic Editions. This comes after the company filed trademarks in Japan back on September 15.
The image closely resembling the handheld was trademarked and it was filed under categories such as “Programs for household video game machines” and “Household video games” as well as merchandise categories like “Key chains,” “Bag charms,” “Cosmetic tools,” and “Clothing.”
— 商標速報bot (@trademark_bot) October 6, 2017
Please keep in mind this is still a rumor and nothing has been confirmed by Nintendo.