It's actually quite impressive they can achieve all this and still only use a 7200rpm spindle speed. With multiple actuators, increasing this speed would effectively multiply the increase by the number of actuators. For example a 2500rpm increase to an overall 10000rpm, would actually be a 5000rpm effective increase since now 2 actuators can utilize this performance.
At least in theory that's how I imagine it working. Might be what they need for larger drives. Regardless its impressive what they've done.