The reality is that nobody really wants SOI, except for high performance CPU vendors like IBM and AMD. And not all CPU vendors want it - Intel, Sun, Fujitsu all passed, as did most low power companies like PA-Semi, Cavium, RMI, etc.
SOI is expensive and isn't very suitable for products with lower margins (e.g. 30-40%), or high volume. It is very useful for space, as SOI has better resilience to SERs than bulk silicon.
So to get additional volume business, GF really needs bulk.
AMD hadn't done bulk in a long time, and their circuit libraries for SOI aren't going to be very helpful for a bulk process as the two behave differently. So they need to spend quite a bit of time getting up to speed there. Right away that means that doing bulk at 40 or 45 is useless, since by the time its production ready, people would be using 32.
Also, note that "32nm" vs. "40nm" is really just a marketing distinction. The only thing that matters are physical characteristics like contacted gate pitch, SRAM density, Ion vs. Ioff, etc. Once upon a time, 180nm referred to a physical characteristic, but 32nm doesn't really. it's more short hand for a certain class of process technologies, but within that class there's a great deal of variation.
For example, IBM's 32nm bulk process has Ion vs. Ioff curves that look a lot more like a Fujitsu 45nm process rather than a 32nm process from TSMC (let alone Intel).
GF has to make some huge investments to compete with TSMC for cutting edge business, and it will probably take 3-5 years to see a pay off. Fortunately, the folks at Abu Dhabi have a long term mindset (I hope) and will see it through.
My guess is that GF will get combined (somehow) with IBM's semiconductor operations to put the R&D under one roof.
one other thing to contemplate is that foundries probably make little money off cutting edge tech, but use advanced customers like Qualcomm, NV and ATI to finance a process which is later sold to other people. i.e. I bet TSMC makes a lot of profit on 130nm and above.
Another issue is whether customers will migrate to newer processes. As design costs go up, fewer and fewer folks will be able to justify moving to a new process. Plenty of folks are still happy with 180nm and may never move (except under extreme duress).
Lots of stuff to think about. Bottom line though is that ATI has a lot of physical design people who will be very helpful for GF in moving to bulk.
DK