The original Tron movie came out on July 2, 1982. While it is considered a flop, it did get quite the cult following, so much so that it garnered a sequel in 2010 called Tron: Legacy. While many of the fans seemed to have issues with it, financially it did very well with an estimated budget of 170 million to make, and grossing over 400 million at the box office.
The team had been coming together to come up with a follow up to Legacy, with director Joseph Kosinki at the helm and stars Garrett Hedlund and Olivia Wilde reprising their roles. The estimated release was meant to be for 2018.
However, the powers that be at Disney have stated that they will not go forward with the idea, focusing more on their live-action remakes of their animated movies than on another sequel. So instead of an original story , we get ANOTHER Alice in Wonderland movie, The Jungle Book, and a remake of Dumbo, which I am especially nervous about. Not to mention the 12 movies expected to be released for the Marvel Cinematic Universe. One Disney executive states that
"Things in the queue got ahead of it and we have such a big slate out in front of it, we started to think, 'Where does it go?' And it's a pretty big investment to make if you are not even sure when you are going to release it."
So they can plan out years of MCU and remake countless cartoons but they can't figure out where to put Tron 3?
Yeah that makes sense.
Disney never did give a formal greenlight for the project, it was just a project that was being discussed. Unfortunately it looks like we have to wait another 28 years to see the grid on the big screen.