It's weird isn't it that each new Tron release gets further and further from actual technological trends like the original was. One thing about Legacy I was disappointed in was that it never acknowledged the internet. But no, instead it ends up completely ignoring modern computing, which is weird given what the original Tron world was supposed to represent. Personal computing was in its infancy in the 80's when the original movie came out. While the visuals were impressive for its time, I think what was far more impressive was the story being told and the possibilities it introduced.
Cloud computing is such an obvious topic that it could touch upon. But my guess is the story will have something to do with AI being manipulated by a 3rd party and a simulation of the real world. I've had a theory that the world being invaded isn't necessarily our world, but an AI recreation.