AMD has previously gone on record saying that they had two upcoming semi-custom deals, one being for x86 and the other for ARM, and that one of these two were not gaming related:
Well, we just found out today that the x86 deal is the one that isn’t related to gaming:http://anandtech.com/show/10268/china-calling-amd-forms-joint-venture-for-x86-server-socs-in-china
That means, of the two, it’s the ARM deal that is related to gaming.
Unless Nintendo does something unusu like not using an AMD chip (which would be very unusual due to their history together), then I do believe it’s practically certain that NX will be using an ARM-based chip from AMD.
We will soon find out.