I have alot of confidence in technology, and it's quick evolution. Moores law is no longer true, as computing power more than doubles every 18 months. I believe i read an article that said computer technology is doubling every 10 to 12 months. I think that we will see that type of memory a lot sooner than you think. In 20 years, imagine what kind of technology will be out there. I simply cannot, as it could be anything!
I also remember hearing how they were trying to harvest swamp micro-organisms and implement them into memory. I'm not sure what happened with that, or if I heard wrong, but apparently it was a very good idea that could have some excellent recourses.