It's really going to be sad to listen to Caroll's final performance as Big Bird and Oscar next year: people have been complaining enough about how "depressed" Big Bird has been sounding in recent years, but the strength in even Caroll's regular speaking voice has weakened significantly as of late - I have to admit, it was difficult to hear him clearly when I met him last year, which I believe was one of the reasons why Debbie answered or finished a lot of questions for him, which is very sweet and loving of her to do. Even during the Q&A panel, he trailed off a bit, and likewise, Debbie finished his story for him.
But either way, we can all say, again, Caroll more than deserves his retirement, and while we may be sad to see him leave, we should be grateful and appreciative of his dedication and hanging in there as long as he possibly could. There will never be another like him, though his characters are in good hands.