I had heard rumors about a sequel ever since they announced TRON 2.0 (originally called Tron Killer App), the video game that "starred" the son of Alan Bradley (Bruce Boxleitner's character).
The rumor was that something would happen on the net (I think some super program, not unlike the MCP, gets released and raises havoc), and Jeff Bridges (or another actor playing the same Flynn character) would lead a team of hackers into the computer to fight it.