From Deadline Hollywood:
This one is a shocker. Veteran crime drama Law & Order will not get its shot at history after all. I hear that after long deliberations, NBC has decided to cancel the long-running procedural, which will end its run at 20 seasons, tied with Gunsmoke. This is very surprising as NBC brass had indicated lately that they would bring L&O for a record-breaking 21st season. But with strong development, especially on the drama side, and soft ratings for L&O, NBC apparently opted not to keep the aging series, which spawned several successful spinoffs. The latest, Law & Order: Los Angeles, will launch next season. L&O's renewal by NBC was also contingent on securing a sizable commitment from the series' cable home TNT whose off-network deal for the show was up at the end of this season.