Honestly it doesn’t look like they are threatened by ARM after all. Qualcomm and Microsoft keep screwing up and I’m not sure who else has both capability and aspiration for PC market. Apple are doing their own thing and not looking back but they’re not going to really threaten x86 in any foreseeable future.
I personally think the threat from ARM (as per current products). There is no reason to get a WoA Snapdragon X device unless you are specifically looking for such hardware.
Snapdragon X devices fails to match x86 (from both Intel and AMD) in terms of performance and efficiency advantages are marginal.
Nvidia and Mediatek's new laptop SoC might have something new to offer.