I think the chances of Sailfish devices made by Xiaomi, and either Jolla or Xiaomi branded are pretty much nil at this stage. Way too big. They'd have nothing to gain.

Oppo / their parent company are exploring all sorts of options ... OnePlus and CyanogenMod ... there are continual rumours about them preparing Ubuntu in anticipation of the Meizu Ubuntu launch being a success ... so it's more likely. But still, Sailfish is pretty ropey, so I think an Oppo or Oneplus branded device is unlikely until the latter half of next year at the earliest. I do hope however that Jolla may be able to make large enough orders next year to use Oppo as their OEM / ODM. A cosmetically altered Oppo U3 would be a great replacement for the existing Jolla - 4.6" 1920x1080 and an octacore ARMv8 Mediatek chip ... though I wouldn't read anything into it, for the conspiracy theorists the U3 is due to launch some time this month or next.