AFAIK, at least for Xbox 360 and PS3, both companies did agree to pay royalties on third-party produced silicon, right? So no worries for the next-gen consoles, and after that, consoles will be just fancy controller units for cloud-based games with little local processing mainly for en-/decoding and DRM enforcement.
That option might exist for the GPU half of an APU, but the CPU half wouldn't fit that arrangment.
Microsoft and Sony owned the IP for the current gen, meaning they could make the chips and do with them as they wished.
If AMD is providing an x86 APU, there is no ownership of the IP for the console makers. They'd need to buy the chip from AMD. What options are left if AMD implodes in two years and it ceases to exist, or due to insolvency triggers a termination clause in the current cross-licensing with Intel?
I suppose AMD could threaten the console makers with its own pending destruction, and goad them into buying six years' worth of APUs in advance just in case...
edit:
That's actually not true at all. That perception is based on the fact that in the previous patent cross license agreement there's a section which governs how the agreement can be terminated, the subsection on termination due to a material breach(the one were the offending party keeps the rights while the other loses them) was followed by subsections on termination due to change of control and bankruptcy. That resulted in people erroneously thinking that a change of control was considered a material breach.(the fact that the agreement was heavily redacted and on a third-party site didn't help either) The newest Patent License actually make this clear.
Interesting, the latest text is more clear on this condition.
It's not very comforting to Sony and Microsoft unless they're the ones buying. They still lose their supplier, and will have to stare down Intel to get things going again.
The possibility exists where there's a corporate re-enactment of the standoff in "The Good, the Bad, and the Ugly" if, say, Microsoft buys AMD, terminating the rights with Intel and simultaneously drawing Sony into the fray.