You are right, Nintendo chose a cheaper older GPU design that was available ONLY in 40nm. We are assuming Sony is going with a design only available at 28nm but if it's part of the 20nm 2014 designs then it may only be available @ 20nm NOT 28 or 32 or 40. 20nm is cheaper if % yields are the same, are they? Will they be the same in 3 months or 6 months, if they will be then it may be worth going with the 20nm node as that appears to be the GloFlo and TSMC node plane for 3 years.
The first part of this post is a contradiction. How can something be a choice if that were the only size available? They could have tried to go smaller if they wanted, but it would have cost more. It's the same reason why we don't see the CPU or GPU smaller than 45nm in the 360.
Which leads me to my next point, yields for 20nm wouldn't be the same, so the cost would not be the same. This is the exact reason why I'm telling you these next gen systems will launch at 28nm and no smaller. Look at the issues companies had reaching 28nm, and you think 20nm would be easily reached at the same cost? Not going to happen and if ban bets were still honored, I would bet you any day of the week.
It really depends on how custom and what building blocks are used. We know Jaguar CPU package are available @ 28nm, will be available at 20nm but not 32nm.
I don't even know the point of this part. All it does is support my view that 28nm will be standard at the launch of next gen.
If the APU, second GPU and common stacked wide IO memory are going to be on the same MCM transposer/carrier then the design is either custom or from a future design. If custom then Sony will bear the brunt of the refresh cost, if a AMD building block then AMD pays and Sony can just order a new custom SoC from AMD built with those new blocks.
It doesn't really work that way. You think Sony is in any position to bear any brunt? Also, AMD is in this business to make money, not pay out of their pocket for Sony's or MS' design. If this is how you think console development is, then you're way off.
AMD is betting the farm on HSA and needs game consoles to jump start the industry. They need HSA accepted so that their Fusion designs can compete with Intel. Without properly written programs taking advantage of AMD GPGPU, AMD APUs can't compete with Intel CPUs. Wide IO because it will be faster, cheaper, require less drive current (DDR4) and less energy.
Intel is so far ahead of AMD there's very little they can do to really compete with them. Staying in the market is what they should be fighting for and I fail to see how consoles would really help out there.
Edit:
Over reacting much?
Stacking is not some science fiction thing, companies are doing it right now while they are preparing for mass market push of this tech. Heck, Vita is using vertical stacking for connecting SoC and video ram.
Yes, but we don't compare handhelds to consoles in hardware design.