Well, Marc Cherry is indeed a Sondheim fan, and a musical theater fan in general. He was at a recent Sondheim benefit in which Felicity Huffman played the interviewer when an actor sang "Franklin Shepard Inc" (can't remember who).
Cherry has said that when DESPERATE HOUSEWIVES is over in 2011-ish, he hopes to write the book to a new Broadway musical.
"Some people can thrive and bloom living life in a living room, that's perfect for some people of one hundred and five. But I at least gotta try, when I think of all the sights that I gotta see, all the places I gotta play, all the things that I gotta be at"