Hypothetically, it's possible for the Super Mario Bros franchise to lose its popularity and grow stale to the point that it's eventually discontinued... but I don't see it happening, at least not any time soon! The character's history has demonstrated that he fits well into a wide variety of games, including platformers, puzzle games, racing games, and even RPGs (in retrospect, it's almost surprising that there hasn't been a Mario FPS!), and the folks at Nintendo have been introducing more than enough innovation into the main series to keep them fresh. Moreover, he's the sort of character that is rediscovered and beloved by a whole new generation of gamers on a regular basis, generations that will subsequently maintain a fond nostalgia for the character. Nintendo will stop making games featuring Mario around the same time that DC stops making comics featuring Superman and Batman!