Credit: Michael Desmond/The CW © 2010 The CW Network Photo: Debbie and Ryan Get Dressed in 90210 Season 3, Episode 9: "They're Playing Her Song"
TVLine has reported that Lori Loughlin (Debbie Wilson) and Ryan Eggold (Ryan Matthews) will not be returning to 90210 for Season 4.
"A 90210 spokesperson confirms that Loughlin and Eggold's contract options have not been picked up and their romantically linked characters — matriarch Deb and teacher Ryan — will exit at season's end. The rep adds that 90210's fourth season will find the West Bev crew transitioning to college, which means there will be less emphasis on teachers and parents."

Source: TVLine