With all the video game characters Disney licensed for Wreck-It Ralph, it seems crazy obvious that they should have brought in Tron, a movie character they turned into a game.
Director Rich Moore shares with ComingSoon.net:
I can't specifically remember why that didn't happen, ...Of course, with a sequel, I'm hoping that we can find a way to see Tron himself in that movie.
Perhaps Disney didn't want to blend brands, thinking that it would be confusing to audiences. Having Tron make a quick cameo would still be fun, though. Let's make it happen, programs.