I think about that often... but especially when I watch the fireworks/parade and Fantasmic.
Despite everything that is "wrong" with DL and DCA I think it would probably bring a tear to Walts eye to see all the innovative things that have been done since he's been gone. Imagine him sitting to watch Fantasmic? I think he'd be thrilled to see how the technology of the time could achieve what it has [a dragon in the middle of the Rivers of Amercia.. etc...] and I also think he'd have a lot of catching up to do since he'd probably be all "Who are these strange characters everyone seems to be loving but I know nothing of..."
Bottom line... I think he'd be proud to know that his Park[s] are still going strong.