How long does it take for the geosynchronous orbit of a satelite to decay to the point where the satelite cra?

A few years, I think, depending on the object's size and its orbital distance. The orbital distance is directly related to the object's orbital speed. Even in earth orbit, there is still a greater density of "air", if you will, than in intergalactic space, or interstellar space for that matter. The friction, and the gravitational influence of the earth, tend to slow the orbital speed if there is no further acceleration of the debris to compensate. So its orbital height will be reduced over time, meaning that it needs greater speed to stay in orbit. Lacking that, the orbital height of the space junk will be reduced, requiring even more speed. And with a lower orbital height, even more friction comes into play, and so on, until it burns up in the atmosphere. We've seen this before. The good news is the odds are that the space junk will most likely either disintegrate upon reentry or hit the Earth's oceans. But your theory of the proliferation of space junk does not hold too much water, it's a big sky. I don't think we could put enough garbage up there to make earth orbit a navigational hazard. Sure, something could hit something, but it is a long shot.