AintitCoolNews reported the plot details to the Tron sequel, which was titled Tr2n at one point and could be Tron 2.0 or some version of that in the future. According to the AICN source, reporting from Vancouver where the movie is being shot, the plot breaks down like this:
The movie starts in 1989. Kevin Flynn (Jeff Bridges) has created some of the world's top-selling games based on his Game Grid challenges in the first film. Flynn disappears, leaving behind his seven-year-old son Sean, and Alan Bradley (Bruce Boxleitner) takes over Flynn's company (ENCOM).
Then the movie jumps ahead to the present:
Sean is now twenty-something. Alan Bradley has info that leads Sean to look for his father in his old arcade -- mothballed. Into the computer world goes Sean. There's a CLU character (Flynn's computer alter-ego from the first film). Flynn has programmed CLU to run around and make a better computer world, but CLU's gone corrupt and is creating his own interpretation. CLU has it out for a kind of program (ISOs) and wants to eradicate them, while the ISOs believe Sean Flynn is the one who will free them from CLU's belligerence. Somewhere in the computer world, Bridges is whizzing around in a classic Light Cycle. Will he help in the battle against CLU?
The source claims the sequel will feature Light Cycles and will be adding Light Jets, which also trail light walls, plus the sequel will feature a huge disc battle.