Exactly. It's also not obvious that the mobile chip market will pay a premium for Intel-calibre fabs. If it won't, then the question becomes whether a TSMC-made Atom is better than a TSMC-made ARM.
It's also fairly common to have custom hardware added to SoCs. Is Intel prepared to open up their processes to that sort of thing?
Unfortunately we can't scale the threshold voltage willy-nilly like in the past because leakage power increases for lower threshold voltages and is now a significant contributor to total power.
This one cuts both ways though. With leakage dominating active power, within a given node, the fabrication process will be relatively more important than microarchitecture, which is a point in Intel's favour.