I would expect that's how they plan on getting to those ridiculous write speeds. Decrease the size of 1 bit so that more of them would fit on one track (a circle on a platter). They would be able to do that since the time to flip the region of the bit would be smaller. However, there is still the problem of finding a material with that much smaller magnetic regions. Which is already a problem in current drives (perpendicular recording) so I don't expect this to fly.