This is disappointing news, to say the least. I wish they could have continued the series, but I will enjoy the remaining episodes and hope for a Blu-ray release.
I think one of the main reasons TRON: Uprising was canceled was because of the dark and serious nature of the series. You have to remember, Disney's core audience is children, which is what the Disney Channel focuses it's programming on. In an effort to expand their audience base, they try to target the tween age (and predominantly male) audience with Disney X D's programming.
However, TRON: Uprising has a more mature tone to it and addresses some weighty and serious themes in the story arc and character development. Because of its mature themes, I think that the decision makers at Disney weren't sure where TRON: Uprising fit in to their programming and demographics, if at all.
People are pointing to Cartoon Network and Nickelodeon as examples: Cartoon Network has Adult Swim. Nickelodeon has Nick At Nite. Why can't Disney do the same? I think the problem is that those networks don't necessarily build their programming model around marketing towards a demographic exclusively made up of children, as they have segments that are marketed to adults (quite successfully). To my knowledge, Disney unfortunately has no comparable analogue.
So I think the decision makers decided to give TRON: Uprising a chance on Disney X D, to see if it could work within the confines of that market demographic. And I think they came to the conclusion that, although it's a fantastic show with amazing artistry, story line, music, etc.., it ultimately just didn't fit into their programming model due to its more mature themes. In other words, they know it's a great series, they just can't show it.
So I think the success of TRON: Uprising was ultimately hampered largely by Disney's exclusive focus on marketing to children and tweens. But that's just the nature of Disney's business. Everything about it is designed for kids. Unfortunately, TRON: Uprising is not.
Who knows, maybe in the future, Disney will start another channel targeted toward adults to compete with Cartoon Network and Nickelodeon. Now that they have acquired the Marvel and Star Wars franchises, shows such as The Clone Wars and TRON: Uprising could help Disney compete with it's competitors for market share. I guess only time will tell.
And to Charlie Bean and all the TRON: Uprising crew that made this incredible show happen, I'm sure many TRON fans will join me in saying "Thank you" for taking us back to the Grid, if only for a short while. Excellent work, everyone! Well done!