From the thoughts of Monty Widenius (MySQL)... What I am looking forward to is diskless computers, a little similar to PDAs today, but with much better capacity. Hard disks will be used more as very large backup devices for things that you don't need regularly.
Battery-backed RAM would be an incredible boost to performance and simplification to implementing ACID transactions. The other big win for large memory databases is to distinguish read-only data, where you could get rid of most semaphores as well. That's not done enough today.
For habit's sake we insist on running OLAP from OLTP systems designed 20-30 years ago. Newer designs can fit far more RO data in RAM too.
(This is a good time to be a computer scientist. Lots of change over the next five years.)