A few points:

- as others have pointed out, the seat map is only somewhat correlated with the number of tickets sold. It is perhaps the single biggest error that new FTers make, in all forums, for all airlines. It only tells you which seats you could request if you were to purchase a ticket at that moment. No airline would place such commercially sensitive information (the exact number of seats sold on any of its flights) on its website. There are some availability tools out there that can tell you if there are 0, 1, 2, 3, ..., 8, or "9 or more" seats available in every booking category. That will give you an idea of what is really available.

For example, I will be traveling YYZ-SYD-YYZ on May 24 and May 31 this month. I few posts up I displayed the availability for the return leg:

J3 C1 Z1 Y0 M0 U0 B0 H0 V0 Q0 L0 A0 R0 K0 N0 E0 S0 T0 I1 P0

The way to interpret this is "There are 3 business class seats for sale (J3). They will sell one at the Z and/or C restricted business price (C1 Z1). There is not a single seat for sale in the economy cabin (Y0). And since economy is sold out, there is also nothing available in the more and more restricted economy fare categories (Y0 M0 U0 B0 H0 V0 Q0 L0 A0 R0 K0 N0 E0 S0)"

However, here is the seat map for the business cabin:

[KVS Availability Tool 3.1.0/Platinum - Apollo Seat Map: 31 May 2008/AC 34/SYD-YYZ/77L/C]
Notice the number of unchosen seats. More than 3! That could mean that people have reservations in business class but haven't selected seats. It could also mean that they have oversold the Y cabin and are holding back some J seats for anticipated upgrades (via certificate or operational). Nobody knows except the airline.

I won't post the Y cabin seatmap, except I can see there are around 30 unselected seats. And yet the availability is Y0.

Conclusion: stop using seat maps to guess your upgrade chances.

How can you increase your upgrade chances to SYD? Keep in mind that this is a really popular route with no non-stop competition, and it avoids the US which is pretty big for some people. One thing you can do is travel on Tuesdays or Wednesdays. Apparently those are less popular business travel days.

Another thing you can do is decide to spend more money and purchase a flexible ticket. It will cost about $5000, but you can confirm the upgrade at booking, if there is upgrade space available. You can see if there is upgrade space by looking at an availability tool and looking for I1 or better.

Yes, $5000 is a lot of money. But they are selling the seat for over $12000 outright, so as long as you can confirm the upgrade at booking, you can look at it as a pretty deep discount business class fare on a very, very popular route.

In this case, if your concern about traveling in Y given your current state of health is worth a few thousand dollars and you can wait an extra day, you could cancel your current booking and book a flexible economy ticket on May 18 and confirm your upgrade immediately.

If you wish to continue purchasing cheaper tickets and hope to use your SSWU, that's fine too. But do expect to miss out more often than not.

Now, there is another way to increase your shot at the upgrade on this route. It will also cost you some money. And that would be to parlay your 3-4 ultra long haul trips into Super Elite status. You must be earning 60-80 thousand status miles per year. If you can find a way to push that over 100k you will be in SE territory and be much higher on the food chain for the upgrades from cheap tickets. If you don't have any place in particular to travel to, you could consider going on trips for no reason other than to earn miles. These are called "mileage runs". I've never done it, but lots of people do. Check out the Mileage Run forum to see what I mean.

If you don't want to do any of these things, you could also consider using other airlines and FF programs to travel to Australia.