I am seeing a miles upgrade offer available for ~63k miles on SFO - DXB. I am at T-48h.

* Assuming there is availability onboard, would it still be the same miles or will there be a better offer?
* At the check-in desk, does anyone have a sense of what would be the cash upgrade cost?
* This is a Prem Flex Plus ticket. Any chance of a complimentary upgrade at all or zero chance?