I'm sure they will find a new material eventually. They may even have 1 material in mind but it may be way to expensive to produce for the mass market use, and some body somewhere may have or may someday soon discover a way to manufacture it cheaper using a new technique which may revolutionize flash memory.
I can see the need for larger then 2GB and I've had bad luck with external hdd's. They never seem to last long, unlike discs and flash memory, and flash memory takes up less room then discs, and may last longer too.