So for the 2009 cross licensing agreement, change of control terminates the cross licensing for both parties[0]. Since there are far more Intel x86 patents in the last 20 years than AMD, sounds like AMD would be the one more at risk, which I think agrees with what you say. In practice, any anti-trust review if Nvidia is the buyer would prevent Nvidia from using it to harm AMD's business.

[0]https://www.kitguru.net/components/cpu/anton-shilov/amd-clar...