But how does one know when actual powerdown condition(power to the circuit) is going to occur, so that pcon bit can be set?
powerdown (going to very low power consumption) "power down" is a misnomer, a tad of power is required to keep the ram contents.
It is not "power down so pcon bit can be set" it is "power down after pcon bit is set"

Is this language or understanding?

Erik