I think in the interests of multiplatform (i.e. PC), they just won't need to go down the many-core route (unless you count the increasingly complex compute shading post-DX11). Even to this day, PC development hasn't really taken much advantage of 8 threads, which is entirely understandable if you look at the steam hardware survey for instance. I don't think the uptake will be that much higher by 2014 either.
That would be incentive enough to have similar numbers of more powerful cores instead of going for 16+ threads. I'd be interested in a developer survey of just what they do on Cell that isn't related to making up for RSX deficiencies and just how much processing time is taken. Cell can do everything, but ultimately, there are choices to be made regarding CPU/GPU budgets, and whether or not it'd be a waste to go with a strong CPU. Hypothetically, if RSX had been a more efficient design, what would Cell be doing now, and would it have been worth it to Sony to produce such a huge CPU over the years?
In the MS GPU job-posting, they do also mention physics, and I do believe there is work with AI on GPU already. Potentially they could just pour all the budget into the GPU compute resources (and by 2014, we should hear much more about DX12), which would give the hardware some legs 5+ years later.
At that point they could just have a relatively straight-forward CPU to handle the basics of the OS and render setup. I suppose there's audio processing as well, though even a dedicated CPU core should be more than enough I would think.. *shrug*