They'd probably try to move all p2p traffic onto the vpn, not just the trackers. That would avoid snooping and throttling by any isp doing deep packet inspection. It would also avoid any one organisation having to pay for all that bandwidth, as well as removing the single point of failure.
However, what's to stop the music industry or Davenport Lyons spending their €5 under an assumed name, and moving into the darknet too? They'd then have access to all the sharers again, and be able to carry on their usual activities.