I feel we are actually pretty close to being able to clean up the space debris. My optimism stems from the lowering cost of getting to space, the availability of light weight space avionics, and vacuum usable adhesives. Small, persistent, delta-v changes can be applied to space junk with lasers and from devices which attach themselves to the junk and lower a tether into the magnetosphere and energize it with a solar cell. Further, on orbit refueling on 'cleaner tugs' becomes more interesting with enough xenon gas stations. NASA did one of their challenges about space junk and it had a number of very creative ideas that were predicated on lower cost access to space.