https://www.avclub.com/gillian-anderson-reiterates-she-s-leaving-the-x-files-a-1821707519

Anderson tells TV Insider (https://www.tvinsider.com/654662/the-x-files-season-11-exclusive-interview-gillian-anderson-david-duchovny/) that she’s “said from the beginning this is it for me. I was a bit surprised by people’s (shocked) reaction to my announcement…because my understanding was that this was a single season.”

You never know nowadays. Until a few years ago most people would have assumed The X-Files was done after its original 9 seasons.