While a 20,000rpm drive might compete on performance with SSDs and offer greater capacity, it would seem to be moving in the opposite direction when it comes to energy efficiency--another chief benefit of the SSD set. Also, heat and noise concerns grow as the revolutions per minute increase. To the end, Western Digital is said to be working on housing that will not only dissipate the heat output, but also dampen the noise. The drive will reportedly feature the same design as the VelociRaptor--2.5-inch platters inside a 3.5-inch enclosure.
It's too early to say when we might see a 20,000rpm Raptor drive, but I would suggest RATT's Round and Round for use in the marketing efforts. When the going gets tough, the tough get hair metal.