My big concern is that we still don't have a solution for https://en.wikipedia.org/wiki/Kessler_syndrome . Lots and lots of small satellites brings us closer to that potential catastrophe. My big hope is that SpaceX's BFR can potentially launch and maneuver cheaply enough to take dead satellites out of orbit in a cost effective manner. Hopefully they manage to launch, and someone is willing to pay to make it happen..…
Cubesats are disposable; they're launched in a way that their orbit decays towards the end of their usable life, at which point they re-enter the atmosphere.