Four Qantas Boeing 787s to be based in Brisbane

That would replace 2 747s. There is still the question of how they retire the 3rd.

8 787s to retire 5 747s. 1 747 is already gone. The 2nd will be going shortly, by the time the 3rd 787 arrives.
The 747 used on 95/96 has already been accounted for. That flight was pulled down to an ad hoc a few months ago. With the aircraft being used as needed on MEL-HKG and MEL-LAX. This 747 has already been covered by the QF9/10 changes and the 1st 4 787s.

They will need to pull a total of 3 747s from the following routes:
BNE-LAX-JFK (daily)
SYD-HND (daily)
SYD-SFO (6 weekly)
SYD-JNB (6 weekly)
SYD-SCL (4 weekly)
SYD-YVR (seasonal)

The current timetables mean the 2 HND aircraft are shared between the SCL and JNB routes.

With the aircraft based in BNE, that more then likely means the BNE-LAX-JFK will change to 787. 2 787s for 2 747s.
A suggested possibility is using 787s 7 and 8 to make a regular SYD-BNE-YVR route, which would leave 5 747s to cover the HND, SFO, JNB and SCL routes with the 6th scheduled for maintenance in off peak times.

True, forgot about that for a moment.
It's been stated that the 2 A380s freed up by the QF9/10 changes would be used for Asia, meaning MEL/SYD-SIN/HKG.
QF127/128, the SYD-HKG 747, is currently seasonal A380 when the 12th A380 isn't in MNL.
If SYD-HKG is made A380 year round, that would free up a 3rd 747 for retirement (but then they would also have a regular A380 and a peak seasonal A380 to assign to other routes)

Thinking a bit more about it, the 'spare' A380 would be put on SYD-LAX to allow QF11/12 to go back to A380 daily (rather then 1 weekly 747). That would cover all the current routes, add a bit of slack into the A380 rotations and give enough 747s for a 4 destination 6 fleet ex-SYD 747 operation (which I was having some doubts about when working on that last post).

Would give:
MEL 4 787 (LAX, PER/LHR), 2 A380 (LAX)
SYD 6 747 (HND, SFO, JNB, SCL), 8 A380 (DXB/LHR, HKG, LAX, DFW)
BNE 4 787 (LAX/JFK, YVR?)
leaving 2 A380 'spare', one of which would be in MNL for heavy maintenance during off peak times.

When QF107/108 was SYD-LAX-JFK, a 747 did the whole flight.
With the extra restrictions QF puts on the LAX-JFK sector, above what the US DOT requires of it, a 747 is too large an aircraft for most of the year.
When they made the transpac changes ~2010, they cut the (old) QF25 from 747 to A330, and ran the A330 on SYD-AKL-LAX-JFK (with a 737 for the MEL-AKL sector of QF25/26),
With the batch of changes that removed AKL-LAX, they only had A380s and 747s going to LAX, and one of those had to go on to JFK and it wasn't going to be an A380.

With the 747 fleet reduction, incoming 787s and the likely BNE-LAX change to 787, they'll only have A380s and 787s going to LAX, one of which needs to go to JFK (unless they cut JFK), and it won't be an A380.