I suppose it depends on just how versatile Zen is, but really, I doubt AMD itself could do it any time soon without someone else taking control. Of all their expertise, they haven't been playing the fanless low power game, and even Intel had stumbles trying to make it work. Haswell-Y was supposed to make fanless ultrabooks big, but it wasn't really until Core M broadwell that they got things rolling.
Qualcomm, on the other hand, might be able to do more with the same tech more quickly just by virtue of existing in a mobile world.
I've only discussed any AMD purchase here in the context of 1) Zen/Polaris failing to regain serious marketshare 2) AMD getting sold not as a whole, but for parts to different companies. In that context, there may well be bargains to be had on different pieces of the company.
Qualcomm is pretty dominant, and even the competition from Samsung and Chinese companies in mobile chips just gives them that much more reason to diversify their offerings and do more than ARM. I think it's very feasible at the right price.
That's what the negotiations are about. AMD tech Intel already uses for Intel tech AMD uses.