them going down or not isn't going to affect the consoles, AMD isn't going to disappear, in worst case, someone will buy them and their contracts will carry over to the new owner. though this new owner might be able to negotiate new terms and change the contract somewhat which might be not as good as before. but there is another issue..
This generation all console makers own the IP to the designs of the console and the custom chips they co developed with the parties involved like IBM and AMD. These new console are using x86 architecture if rumors are true, which is licensed to AMD, seems impossible for the platform holders to own the designs because it's someone else's design, and that someone else never is selling this IP. things might get complicated down the road, this generation platform holders needed to work with AMD/IBM/NV for redesign and other revisions not for production of the chips which they owned. if something happens to AMD it can be a pretty horrible licensing nightmare with other parties involved.