the xbox 360 came in my mind, remember when it change last minute from 256 MB of GDDR3 to 512? this was very costly at its time, as microsoft admits, but they were force by EPIC
they used to make those kind of things, maybe they have done another last minute change
what if the mainboard was flexible enough to permit DDR3 or GDDR5, and one/two APU?
it's reasonable that they're gone with this first type of solution to be able to such last minute change "reaction"? future revisions can shrink component and cut useless features to save the cost
The issue I see with a dual apu setup is that it is very wasteful. If they have the ability to connect a hi-speed link to the apu, it seems the budget would be better spent in connecting to a beefier gpu instead of a duplicate apu.
The gpu is the weaklink in the rumored durango design, not the cpu, so doubling up on cpu resources would be wasteful, unless they feel they need extra compute for kinect, but I would think their compute needs for kinect would be better served with CU's rather than CPUs.