VS200 reward availability

It's been a while....(new addition to the family has limited travelling opportunities)
Anyway, I have a work trip to HK in 5 weeks time
(though I depart on Valentines Day, so the OH is a bit grumpy). My company are prudent/stingy when it comes to what class you can book into. We can fly PE for flights >8hrs, but most colleagues fly Cathay, which I find odd, as they don't have PE, so end up in Economy :-S (imagine it's the fact Cathay operate several flights a day to HKG versus VS's one). That said, there is an unwritten rule to minimise the cost of travel, however I have managed to get a great price with an S fare on the outward leg. I have plenty of miles stashed, but having spoken with CS, there is no G availability at the moment. They said the flight is quiet at the moment, so I should check regularly as availability could change.
So, two questions:
a) Are there any points between now and the departure date when it is most likely that availability will change.....or is it pot luck?
b) What is the likely cost for the extra tax etc?
and a cheeky third question.....if my luck doesn't extend to utilising my miles for an upgrade into G, might a friendly v-flyer fancy a CH companion on Valentines evening?!?
Thanks in advance
Anyway, I have a work trip to HK in 5 weeks time

So, two questions:
a) Are there any points between now and the departure date when it is most likely that availability will change.....or is it pot luck?
b) What is the likely cost for the extra tax etc?
and a cheeky third question.....if my luck doesn't extend to utilising my miles for an upgrade into G, might a friendly v-flyer fancy a CH companion on Valentines evening?!?
Thanks in advance
