I think Apple's play in the low power / ULV chip world is going to be the MBA for a while longer, and maybe this Tablet if/when it makes it to market (as some sort of device that competes in a loose sense with netbooks but is not really a netbook itself). As far as designs more like that Asus, I've been wrong, and I'm sure it's technically possible, but I don't see them releasing a notebook that weighs almost 5 lbs and using a ULV in it.
With the motion of OS X into efficient use of multiple cores and all the additional technologies that have been added since Panther, and with the amount of processing intensive work that gets done on Macs, it seems to me that the issue is just going to be that Macs can use as much more processing power as they can get, and so Apple will continue to try to use relatively faster processors predominantly.