I’ve heard gossip that there might be a spin-off with Cady as the main character.
Do not mourn too much the termination of Longmire after six seasons. That is a success in the TV business and long enough to earn its main actors years of residuals. With a few exceptions, series TV shows have a lifespan of five to seven years, after which they exhaust their premise and lose audience interest and ratings. Even with a top notch staff of writers and free-lancers, it is hard to come up with seven years -- 154 episodes -- of a TV show without repeating old plots and dialog.
In addition to lingering plot lines, my major gripe against Longmire is that, like many detective shows these days, it developed a coziness with its major characters and had politically correct comments and plot points. The best detective and crime shows though are consistently based on sharp-edged plots that have the protagonist isolated and struggling with bad people, indifferent good people, and unreliable friends and allies. Get away from that too much and you end up with something that conveys no more sense of menace and human rottenness than an cartoon featuring the Scoobie gang.