On September 3, a couple of weeks before its premiere, Deadline announced that Season 23 of "Law & Order: Special Victims Unit" would air sans Jamie Gray Hyder and Christian Garland actor Demore Barnes. The following day, Hyder shared her perspective on this development to her personal Twitter account. Her response predominately consisted of a screenshot of the article's headline and a personal statement reading in part, "It is with a heavy heart that I confirm Kat's departure from the squad room. The decision was made above my pay grade, and wouldn't have been my choice. But hey — that's show biz for ya."
A couple months later, Hyder elaborated on her "SVU" departure in an interview with Entertainment Tonight, when asked how she felt about the end of Kat's time on the series. "The No. 1 thing you have to learn, if you want to go into show business, is that a majority of decisions that are made that impact you usually have nothing to do with you," Hyder said. "It's a hard reality, but one that you're serving yourself better the sooner you can get that in your head."
So, while the exact reason for "Law & Order: SVU" continuing without Hyder remains a mystery, it's relatively safe to assume that if its producers don't want Kat back for another season now, she's most likely gone for good.