"We have an idea and an approach and a way into it that I am really excited about, and now it's about execution on the level of the script. So working hard on that in the background, and hopefully that'll all come together.
"It's still the same plan in that Tron 3 would deliver on the promises set up at the end of Legacy in different ways.
You look at what happened in the closing scenes of Legacy - I think it sets a clear direction for what could happen in the next chapter," Kosinski added.
Tron: Legacy star Garrett Hedlund was recently confirmed for the sequel.
Kosinski's next movie will be the Tom Cruise-starring Oblivion, which releases on April 12, 2013.