Brittany Murphy and Johnny Hardwick both Passed Away, Murphy in 2009 before the original shows ending, and Hardwick in 2023 after recording a few episodes
Tom Petty, who voiced the character of Lucky, passed away in 2017. Lucky's wife Luanne, voiced by Brittany Murphy, passed away in 2009. It's a high chance that they'll be mentioned in the revival, but may not appear at all.