This is an application, not a granted patent, and there's no guarantee that it will translate to a finished product. Nintendo originally filed for this patent in Japan in March 2017 -- if there's anything in the works, it might take a while to show up. There are also technical challenges to overcome. Smartphone cases tend to be model-specific. Would Nintendo release a variety of cases to support the most popular phones, and would it release updated versions to make sure you can keep playing after a phone upgrade? If it only released cases for a single generation of phones, you might only get a few years of play time.

Still, this would address demand for a Game boy revival without requiring an entirely separate (and more expensive) gadget. You could relive the Pokémon battles of your childhood and check your Instagram feed on one device in your pocket.