"Would a dedicated fab using TSMC be a good investment? seems to me either they go with Intel or build a dedicated fab with TSMC. Comments?"
[You build a dedicated TSMC fab based on what technology? The 28nm they still don't have fully ramped? And be instantly obsolete? Or the 20nm that may not exist in volume for three years? And be obsolete then? Apple loses either way with a deal with TSMC as Intel leaves TSMCs fabrication in the dust. ARM foundries are so far behind they they have to attempt to skip cycles. They can't even demonstrate a proper ramp when they don't skip cycles. Intel is on its second ramp of FinFET. This will not end well for ARM or its foundries. It's all about the fabrication. Intel's lead is insurmountable. I'm guessing that Apple has already figured it out....]
The problem with TSMC is no FinFet technology. TSMC's 20nm is designed for low power at the expense of Performance. Which means that ARM chips manufactured with TSMC will not have the Performance of an ATOM.
Intel is in the drivers seat when it comes to Power and Performance. Thats why Apple will go with Intel. Better chips at a competitive price and reliable delivery. No one else can do this.