Well, Gordon will undoubtedly play through next year. He is under a guaranteed contract through 2019, with a $4 million buyout for 2020. The Royals will surely pay the $4 million then and say good-bye.
Gordon has not been the same player since he tore his groin in 2015 (3 years ago today, coincidentally). We all remember the critical home run in game 1 of the World Series that year; but even with that key moment, you can see the sharp drop-off in his offensive production beginning with his return from that injury.
That said, Gordon probably doesn't even crack the top 10 when it comes to the things wrong with the Royals this year. I would say they're unwatchable - but that's not true. There is a certain amount of gallows humor in watching to see how purely awful they can be.