imdb.com says that 'The Champion' had a length of 31 minutes. The review on DVDBeaver.com says it is only a 9:22 excerpt
http://www.imdb.com/title/tt0005074/
http://www.dvdbeaver.com/film/DVDCompare/citylights.htm
This link suggests that 'The Magnificent Ambersons' will still be released on Blu-ray in 2012 --
http://www.nypost.com/p/blogs/movies/dvd_extra_lacava_clara_bow_and_other_KKx5ndxJs4SxsVZzmGfECI
Still, one would think that it would be noted on one of these sites, but it's not --...
'The Magnificent Ambersons' is (still?) available on WBShop --
http://www.wbshop.com/product/magnificent+ambersons+the+1000202178.do?sortby=ourPicks&from=Search
Yet, there are no results for 'Ambersons' on WarnerBros.com --
http://www.warnerbros.com/search?start=0&q=ambersons...