To summarize, Disney began work on a sequel to Tron: Legacy immediately. Legacy was meant to kick off a larger universe of movies and TV. As time went on, other expected hits flopped, and Disney acquired Star Wars and made it their new darling, the Tron sequel got shelved.
Jared Leto, who was going to have a minor role in Tron: Ascension, pushed to have a new movie made anyway, making his character the star. The result is that what was more of less going to be the third act of Ascension was fleshed out into a whole movie minus Sam Flynn, Quora, and Tron.
Imagine if Return of the Jedi was never made. Instead, the third act of the movie, the attack on the second Death Star, was turned into a whole movie but the continuation of the plots involving Han Solo, Darth Vader, and Luke Skywalker were completely cut out. Then Wedge Antilles was made the star of the movie and he personally confronted Chancellor Palpatine and saved the galaxy. That’s pretty much what has happened to the Tron franchise. :(
The problem with your Return of the Jedi analogy is that in the Tron world there wasn’t a Han Solo, Darth Vader and Luke Skywalker story to continue in Tron.
Everything in Tron Legacy was completely contained to Legacy and the ending of the movie didn’t leave much to be explored.
There ending was an ISO that is now in the real world. Soooo other than a fish out of water that has a great ass, what is the story to be continued?
The bad guys in Legacy were completely nebulous and they certainly didn’t pose any sort of threat to the real world. All they ever did was destroy thier only bar.
In case it wasn’t obvious;
Han Solo = Tron. He was defeated, but not dead and Legacy hinted that his reprogramming had worn off.
Luke Skywalker = Sam Flynn, the son inheriting his father’s legacy (powers).
Darth Vader = Edward Dillinger Jr., the foil for Sam Flynn. The whole after credits scene in Legacy set him up for a showdown with Sam and Quora.
Tron was always a classic good vs evil story that parallels Star Wars pretty heavily. Right down to Jeff Bridges in Legacy being called a “Stoner Jedi.” An Empire (the MCP/Clu) oppressing an entire universe of beings and how a rebellion rose up to overcome them.
Edward Dillinger jr was played by Cillian Murphy in an uncredited role. The character didn’t exist.
Tron was also non existent in legacy. He had a single line.
None of these storylines you are talking about existed. A post credit scene is fluff.