Mike Judge made a new Beavis and Butt-Head movie, which led to the show's third revival. Pamela Adlon's voice-over career is pretty consistent.
Though I still think, if they could find an actress who can mimic Brittany Murphy's signature voice, they could recast her role for a one-shot appearance... unless maybe the new gal has a deeper voice, and they justify it by saying Luanne's become a chain-smoker in the interim and it's given her "grown-up pipes".[
1] Another possibility: Luanne, unable to make it to her aunt and uncle's house for a visit, sends along the children [yup, at least three; she and Lucky are a loving couple]. Gracie, the eldest, squeaks and giggles when she's excited, just like her mother. Respectful, but quite funny.