It is true that storage media are becoming cheaper and cheaper... It's just how the industry "accepts" or "rejects" these ideas...
Memory cards have come a long way in a very short span of time, but remember that optical discs are still the best way of storing data/movies/music for long periods of time.
A new way of storing memory cards will have to be invented such as "anti magnetic" or "anti static" containers or even "anti-shock" systems... if you drop a memory card or put it near a magnet, there's a big chance of spoiling its contents when compared to optical discs - right?
I think the advent of memory cards for movies will be feasible about 5 years down the road (guesstimate of course).