Apparently Wreck-it-Ralph was such a big hit for Disney, which is unsurprising, that a sequel has been confirmed and Mario is going to be in it. When I first heard the news my reaction was a giant cringe. Unfortunately, at least in my mind, Disney does not have the best track record with sequels. Many of them weren't even released for movies but rather directly to dvd. Cinderella II was atrocious in that it wasn't even a full length film but rather a compilation of shorts.
It will largely depend on what the plot will be. In the first film the issues of the characters seemed to be largely resolved which causes an issue for the second film. The most interesting part of a story is watching how a character develops and resolves, which is something that is done well in the Pixar sequels of Toy Story. If the game worlds are just having a crises and the movie becomes just a hero movie in which the characters have to save the world, the movie will become very bland.
Disney has brought on John Lasseter as a story consultant so there is still hope for a good story. Ideally though, I would prefer Disney to make a new movie, especially seeing how Dreamworks and Blue Sky are stepping up their game.