They're trying to extend her contract, but to be fair I wouldn't be surprised if she does leave, mostly because the average amount of time a cast member usually spends on SNL is usually 7 seasons (hey I got bored one day and thought I should see if there's a mean, median, and mode within the people that have appeared on the show), and she's been on for seven and a half (she came on in late season 36, just as Kristin Wiig was on her way out, I think Kate's first episode was Sofia Vergara/One Direction
https://variety.com/2019/tv/news/kate-mckinnon-contract-saturday-night-live-1203200109/?fbclid=IwAR3Xe61cKxbEfAcAWAmBuDFv5yBNbIMeilLjGeZwCFw0Z4lWxGPqVKJSjKs
actually come to think of it this is Aidy Bryant and Cecily Strong's 7th season as well, well, we'll have to find out around the time the season finale airs in a couple of weeks