Solid state drives may have their benefits when it comes to reliability, speed, low power consumption, and small dimensions. But the storage market is mainly driven by cost-per-gigabyte, and in that regard, SSDs still can't compete with traditional spinning hard disk drives.
In light of this, Western Digital is reportedly developing a 20,000rpm Raptor hard drive - twice the speed of its current Raptor lineup - to counter the increasing popularity of SSDs. The drive is apparently a 2.5-inch model with a custom 3.5-inch 'caddy' similar to that of the recently announced VelociRaptor, which will act as both a heatsink for cooling and provide a stiff frame to counter vibration and to help with noise-reduction as well.
One particular drawback in today's energy-conscious times, however, is that a 20K drive would need more electricity to spin it. But I can imagine enthusiasts who demand nothing but the best when it comes to performance would gladly buy one of these beasts.