You’re already seeing the normal Qatar pattern. The price drops in steps, then suddenly stops or disappears.
€1500 for business on a 14 hour sector to Sydney is actually very reasonable by Qatar standards. That’s the leg that matters, and that’s where the value is. The 6 hour hop to Doha is nice in business, but not essential.
A few things to keep in mind:
Prices often keep dropping until about 3 to 5 days before departure, then either freeze or vanish
Gate or check in upgrades are hit or miss and not guaranteed to be cheaper
If business is filling up, upgrade offers can disappear overnight
If the system lets you upgrade only the DOH–SYD leg, that’s the sweet spot. Sometimes it’s possible online or via app, sometimes not.
If €1500 is within your comfort zone and you’d be happy locking it in as a birthday gift, I wouldn’t wait much longer. Waiting might save a little more, but it also risks losing the offer entirely.
Worst case, if you wait, check daily and be ready to pull the trigger fast.