I hadn't thought of that, but you're right. They did reuse old songs, but they were all redone. That is one way "The Street We Live On" was an improvement there. They showed a lot of old clips. I liked how at the end, they had a clip for each year. I think for the 40th Anniversary, they could do something like that, but expand on it, rather than mushing it all together at the end, they could base the whole show on that and show a few minutes worth of clips for each year.
In fact I have a Peanuts book where they have quite a few pages worth of strips for each decade. I could see "Sesame Street" doing something like that in form of a TV special.
Another thought, even though I feel that Abby has been overused, I'm thinking maybe focusing on her for the 40th Anniversary would work. She wouldn't know about "Sesame Street's" history, so maybe somehow she could learn about Mr. Hooper and the revealing of Snuffy to the adults, etc. I mean, I wouldn't want it to be "The Street We Live On" all over again, but maybe they could add more. Like that fan fiction somebody wrote about Grover taking Elmo through history with his time machine, starting with them meeting the original orange Oscar. Grover, Elmo and Abby could all go on the ride there. Just a few thoughts I had. I might write more as I think of more ideas.