Blu is the only way forward
Anyone that predicts that downloads are going to take off, or that we will have movies in temporary form on memory cards is living in cuckoo land, Sony hate land, or denial.
People like disc formats, they like something to hold, they like to show their movie collection to friends, they like their shelves full of movies they own, movies they can pickup and feel, movies they can browse.
Most people don't like the idea of digitally renting a movie, let alone digitally buying a movie, with it's DRM restrictions, and locked to an account, and stored on someone else's server.
Downloads will be a niche for the forseeable future for the reasons above (and not even talking about the lack of infractructure to support HD downloads). Flash cards will never take off, and is just a lame idea from the outset.