Obviously this would take some time to develop (years?), but this is potentially fantastic news for Apple. In the current context, I'm sure almost everyone would agree that a custom ULV Sandy Bridge chip stripped of its graphics core, clocked a bit higher, and coupled with a 3rd-party alternative would make a new line of MBA's unbeatable.
But moving forward, hopefully Apple can find ways to streamline its own processes while stripping away general-purpose silicon from Intel parts. If so, we could see smaller dies, lower power consumption, and higher clock speeds for Machines running Mac OSX.
The downside is that this could really hurt the Hackintosh community. People will make it work, but it will be less convenient than it is now.
Not sure it would be worth Apple's while to do this directly, but the interesting possiblity would be nVidia they don't have their own fabs anyways. So why not take their GPU cores and IO silicon team it with a couple of sandy bridge CPU cores and produce a single chip x86 SoC.
nVidia would be able to push them for lots of other uses basically anywhere they are using Ion Platform now. So they have a much bigger market to drive a move here. I'm sure they could maybe Talk Apple into pre-buying all the top bins for the next macbooks, teaming them with dedicated GPU in the upper end.