I went looking at Disney's home site for their home entertainment division (
http://disneyvideos.disney.go.com/, found via Google), to see what release plans they had, as I was specifically looking for "Mary Poppins". I believe that film would look and sound absolutely awesome on Blu-Ray, and it is a great movie for its genre.
When I didn't see it listed, I found a "contact us" link on the site, and wrote them, asking to consider releasing it on BR.
I actually got a letter back from them saying they would forward my suggestion to the appropriate folks at Disney.
So, all I can say is WRITE. It not only might get us some content we want from the catalogs out there, but it also reinforces the audience for BR material.
Thanks.