SSDs are fast, but they're still orders of magnitude slower than RAM in terms of latency. Keep in mind, back in the day, the spread between dram and spinning disks wasnt as bad as it is today.
The next great performance challenge may be the so-called "memory wall" wrt the performance of CPUs vs the performance of RAM. Id be curious to see what that would do to performance if it underwent the same dramatic improvement as nonvolatile storage.
We may actually see them both happening at once; one of the things R. Stanley Williams talks about in his excellent memristor talk is a method they developed for stacking hundreds of chips on top of a processor, which he says may end up providing just as much benefit as the memristor itself.
The possibilities that could be opened up by having a terabyte or more of extremely fast non volatile storage attached by a bus as large as you care to make it directly on top of a CPU are mind boggling.
Then when you consider that you can use them as FPGAs for computation instead and dynamically reconfigure them... wow.
Memristors are only a year or two away from commercial availability, though it will probably be a while after that until they live up to the hype. We live in exciting times.
FWIW, although it is no doubt not an apples/apples comparison[1], todays faster SSDs (~500MB/s) have roughly the same bandwidth as pentium-era PC-66 ram, while todays faster DDR3 is >12GB/s (which i guess doubles with dual channel). So its not 100% crazy.
The next great performance challenge may be the so-called "memory wall" wrt the performance of CPUs vs the performance of RAM. Id be curious to see what that would do to performance if it underwent the same dramatic improvement as nonvolatile storage.