Casablanca is coming to Blu-ray, but it's release on HD-DVD was an experiment, it crashed and burned, that's why we saw so few 'classics' released after it.
Most of the major classic movies you can think of are currently being restored to bring them upto scratch, so they couldn't be released at this time.
Ironically the titles in the worst state are those from the 70's and 80's due to low quality film stock.
There's some info here:-
Personally I'm not interested in much prior to the 70's.