According to longtime franchise lead, Neve Campbell, she is no longer coming back to the Scream franchise following her appearance in this year's Scream reboot. As per Vanity Fair, Campbell is not part of Scream 6 after the Scream star due to low pay.
Specifically, Campbell said in her statement, "I felt the offer that was presented to me did not equate to the value I have brought to the franchise."
Neve Campbell is best known for her role as Sidney Prescott in the Scream franchise. She is the quintessential "final girl" and effectively gave birth to the trope best defined as the last character left alive to face the usually masked culprit in any Slasher Movie.
So far, Campbell has appeared in all five Scream films, including the one that premiered to box office success earlier this year. However, unlike the first four installments, Scream 5's masked assailant was not connected to Campbell in any way - the duo are just fans of the in-universe Slasher franchise, Stab.
It's unfortunate that conflict about pay is what ultimately took down Sidney Prescott. The latest Scream film had an excellent passing of the torch moment between the longtime final girl and the successor, Melissa Barrera's Sam Carpenter, who is the illegitimate daughter of Billy Loomis. It would have been awesome to see her reprise her role even if in a somewhat reduced capacity to reflect the lower pay. But, ultimately, Campbell is right to demand what she feels she is owed.
As for Scream 6, Courteney Cox, who plays Gale Weathers in all five Scream films, confirmed earlier this year that the next Scream movie will start production this summer. This would give the returning directors, Matt Bettinelli-Olpin and Tyler Gillett, plenty of time to work on the upcoming installment ahead of its release next year.