While some are acting as if this news is shocking, it really isn't a surprise to learn that Disney has decided against a sequel to Tron: Legacy. The third film in the Tron franchise was to reunite director Joseph Kosinski plus stars Garrett Hedlund and Olivia Wilde, and enough prep had been put into that the title Tron: Ascension was already being floated, and a start date set for this fall. Apparently Jared Leto was also being pursued for a role. But all of that was for naught, it seems.
The reasons for Disney's decision are unclear, and THR doesn't offer any additional info. Still, it's pretty easy to figure out why. Tron: Legacy cost a pretty penny to produce, close to $200M, and while it earned $400M worldwide, it didn't inspire a lot of excitement from anybody. Talk of a third film went on for years with little movement, and the sudden to decision to move forward came out of the blue.
It's possible Disney got cold feet after another futuristic film, Tomorrowland, tanked at the box office. Whatever the reason, Tron has had the plug pulled on it once and for all.